Insulin-like factor 3 levels in cord blood and serum from children: effects of age, postnatal hypothalamic-pituitary-gonadal axis activation, and cryptorchidism

Impact of Obesity on Pubertal Timing and Male Fertility

Childhood obesity has profound effects on puberty in boys and girls, altering its timing, progression, and associated hormonal changes. Also, later male fertility could be impaired by childhood and pubertal obesity in light of the impact of inflammatory markers on semen quality. The aim of this narrative review is to explore the intricate relationship between childhood obesity and its impact on pubertal development and fertility, with a specific focus on boys. Such a relationship between obesity and pubertal timing in males is highly influenced by metabolic, hormonal, genetic, epigenetic, and environmental factors. While many studies suggest that obesity accelerates pubertal onset in boys, some studies do not confirm these findings, especially in cases of severe obesity. In fact, delayed puberty has also been reported in certain instances. Obesity influences fertility through different central and peripheral processes, including an altered endocrine milieu, inflammatory environment, and epigenetic modifications that alter semen quality and vitality, leading to subfertility or infertility. The early identification and management of potential issues associated with obesity are crucial for ensuring optimal reproductive health in adulthood. Further research is essential to clarify these associations and to develop targeted interventions aimed at preventing the negative health outcomes associated with obesity-related disruptions in puberty and fertility.

Insulin-like peptide 3 (INSL3) as an indicator of leydig cell insufficiency (LCI) in Middle-aged and older men with hypogonadism: reference range and threshold

Insulin-like peptide 3 (INSL3) is a circulating biomarker for Leydig cell functional capacity in men, also indicating Leydig Cell Insufficiency (LCI) and potential primary hypogonadism. Using results from large cohort studies we explore sources of biological and technical variance, and establish a reference range for adult men. It is constitutively secreted with little within-individual variation and reflects testicular capacity to produce testosterone. The main INSL3 assays available indicate good concordance with low technical variance; there is no effect of ethnicity. INSL3 declines with age from 35 years at about 15% per decade. Like low calculated free testosterone, and to a lesser extent low total testosterone, reduced INSL3 is significantly associated with increasing age-related morbidity, including lower overall sexual function, reflecting LCI. Consequently, low INSL3 (≤0.4 ng/ml; ca. <2 SD from the population mean) might serve as an additional biochemical marker in the assessment of functional hypogonadism (late-onset hypogonadism, LOH) where testosterone is in the borderline low range. Excluding individuals with low LCI (INSL3 ≤ 0.4 ng/ml) leads to an age-independent (> 35 years) reference range (serum) for INSL3 in the eugonadal population of 0.4 - 2.3 ng/ml, with low INSL3 prospectively identifying individuals at risk of increased future morbidity.

Maternal Fed Zinc-Deficient Diet: Effects on Relaxin Family Peptides and Oxidant System in the Testis and Liver Tissue of Male Offspring

Today, the studies are limited on roles of insulin-like peptide 3 (INSL3), insulin-like peptide 7 (INSL7), and relaxin family peptide receptor 1 (RXFP1) which are synthesized by the testis. It is aimed to investigate the levels of the sex hormone as testosterone and the family of insulin-like proteins (relaxin family peptides), which are important in the puberty transition, in the testicular and liver tissues of male offspring born to female rats fed a zinc-deficient diet during the pregnancy, and in the changes in lipid peroxidation markers. The study was performed on 40 male offspring. In Group I: Control group, both male offspring and mothers were fed with standard rat chow. In Group II: Zinc deficient diet, both male offspring and mothers were fed a zinc-deficient diet (2.8 mg/kg zinc). In Group III: Normal diet, male offspring fed standard rat chow for 45 days (66th day) after being separated from their mothers with a maternal zinc-deficient diet. In Group IV: Zinc-supplemented diet, offspring fed with zinc supplemented (5 mg/kg/day intraperitoneal zinc sulfate, i.p.) in addition to standard rat chow after being separated from their mothers with maternal zinc deficiency until the termination of the study (66th day). Our study suggests that zinc-supplemented diets play an important role in the changes in INSL3, INSL7, RXFP1, and testosterone levels during spermatogenesis. INSL7, INSL3, and RXFP1 levels were higher in zinc-supplemented group than the zinc-deficient diet group. Liver levels of INSL3, INSL7, and MDA were significantly different in zinc-deficiency diet group than zinc-supplemented group.

A Therapeutic Proposal for Mini-Puberty in Male Infants with Hypogonadotropic Hypogonadism: A Retrospective Case Series

Background: Male patients with congenital hypogonadotropic hypogonadism (CHH) have impaired postnatal activation of the hypothalamic-pituitary-gonadal axis that occurs during mini-puberty. The aim of this study was to report our experience using gonadotropin replacement therapy for mini-puberty in male infants with CHH and to establish treatment recommendations. Methods: The patients included in this retrospective case series (n = 9) were diagnosed in the postnatal period due to micropenis, with two being accompanied by cryptorchidism and four with other associated hormonal deficits. All patients started treatment with gonadotropins early after diagnosis, between 2 weeks and 5 months of age, with a schedule of discontinuous injections with subcutaneous human chorionic gonadotropin (62.5-500 IU) two times per week and recombinant follicle-stimulating hormone-alpha (37.5-75 IU) three times per week. Results: The data from our study show an early response, ranging from almost undetectable levels of testosterone at diagnosis to elevated levels after starting treatment, as well as a positive clinical response with increases in testicular volume and penis size in all cases without requiring complementary treatment with testosterone esters and without adverse effects. Conclusions: Our results show that gonadotropin replacement therapy is a well-tolerated and effective treatment for testicular and penile problems in male patients with CHH.

Exploring Testicular Descent: Recent Findings and Future Prospects in Canine Cryptorchidism

BACKGROUND

Canine cryptorchidism, manifested by an abnormal testicular position, poses significant health risks and reproductive challenges in affected males. Despite a high prevalence, estimated at up to 10% in the canine population, a comprehensive understanding of its pathogenesis remains elusive. Studies in human cryptorchids and knockout mice have identified key factors involved in testicular descent, including INSL3, RXFP2, and AR. To date, only three DNA variants, found in the RXFP2, HMGA2, and KAT6A genes, have been associated with canine cryptorchidism.

SUMMARY

This review briefly summarizes current knowledge on testicular descent and the factors that regulate this process, based on cryptorchidism in humans and mice. It also highlights recent findings related to canine cryptorchidism, focusing on the INSL3, HMGA2, and KAT6A genes. The most significant results are discussed, with an emphasis on the role of the epididymis in testicular descent. This report presents insights that may facilitate further research aiming to broaden our understanding of canine cryptorchidism pathogenesis.

KEY MESSAGES

DNA polymorphism in the KAT6A gene, associated with changes in global H3K9 acetylation, as well as the DNA methylation pattern in the INSL3 gene, suggest that further research should strongly focus on epigenetic modifications. In addition, the development of the epididymo-testicular junction and the link between cryptorchidism prevalence and dog size should be further investigated.

Mini-Puberty, Physiological and Disordered: Consequences, and Potential for Therapeutic Replacement

There are 3 physiological waves of central hypothalamic-pituitary-gonadal (HPG) axis activity over the lifetime. The first occurs during fetal life, the second-termed "mini-puberty"-in the first months after birth, and the third at puberty. After adolescence, the axis remains active all through adulthood. Congenital hypogonadotropic hypogonadism (CHH) is a rare genetic disorder characterized by a deficiency in hypothalamic gonadotropin-releasing hormone (GnRH) secretion or action. In cases of severe CHH, all 3 waves of GnRH pulsatility are absent. The absence of fetal HPG axis activation manifests in around 50% of male newborns with micropenis and/or undescended testes (cryptorchidism). In these boys, the lack of the mini-puberty phase accentuates testicular immaturity. This is characterized by a low number of Sertoli cells, which are important for future reproductive capacity. Thus, absent mini-puberty will have detrimental effects on later fertility in these males. The diagnosis of CHH is often missed in infants, and even if recognized, there is no consensus on optimal therapeutic management. Here we review physiological mini-puberty and consequences of central HPG axis disorders; provide a diagnostic approach to allow for early identification of these conditions; and review current treatment options for replacement of mini-puberty in male infants with CHH. There is evidence from small case series that replacement with gonadotropins to mimic "mini-puberty" in males could have beneficial outcomes not only regarding testis descent, but also normalization of testis and penile sizes. Moreover, such therapeutic replacement regimens in disordered mini-puberty could address both reproductive and nonreproductive implications.

Inhibition of WNT/β-catenin signalling during sex-specific gonadal differentiation is essential for normal human fetal testis development

Sex-specific gonadal differentiation is directed by complex signalling promoting development in either male or female direction, while simultaneously inhibiting the opposite pathway. In mice, the WNT/β-catenin pathway promotes ovarian development and the importance of actively inhibiting this pathway to ensure normal testis development has been recognised. However, the implications of alterations in the tightly regulated WNT/β-catenin signalling during human fetal gonad development has not yet been examined in detail. Thus, the aim of this study was to examine the consequences of dysregulating the WNT/β-catenin signalling pathway in the supporting cell lineage during sex-specific human fetal gonad development using an established and extensively validated ex vivo culture model. Inhibition of WNT/β-catenin signalling in human fetal ovary cultures resulted in only minor effects, including reduced secretion of RSPO1 and reduced cell proliferation although this was not consistently found in all treatment groups. In contrast, promotion of WNT/β-catenin signalling in testes severely affected development and function. This included disrupted seminiferous cord structures, reduced cell proliferation, reduced expression of SOX9/AMH, reduced secretion of Inhibin B and AMH as well as loss of the germ cell population. Additionally, Leydig cell function was markedly impaired with reduced secretion of testosterone, androstenedione and INSL3. Together, this study suggests that dysregulated WNT/β-catenin signalling during human fetal gonad development severely impairs testicular development and function. Importantly, our study highlights the notion that sufficient inhibition of the opposite pathway during sex-specific gonadal differentiation is essential to ensure normal development and function also applies to human fetal gonads.

Role of NR5A1 Gene Mutations in Disorders of Sex Development: Molecular and Clinical Features

Disorders/differences of sex development (DSDs) are defined as broad, heterogenous groups of congenital conditions characterized by atypical development of genetic, gonadal, or phenotypic sex accompanied by abnormal development of internal and/or external genitalia. NR5A1 gene mutation is one of the principal genetic alterations implicated in causing DSD. This review outlines the role of NR5A1 gene during the process of gonadal development in humans, provides an overview of the molecular and functional characteristics of NR5A1 gene, and discusses potential clinical phenotypes and additional organ diseases due to NR5A1 mutations. NR5A1 mutations were analyzed in patients with 46,XY DSD and 46,XX DSD both during the neonatal and pubertal periods. Loss of function of the NR5A1 gene causes several different phenotypes, including some associated with disease in additional organs. Clinical phenotypes may vary, even among patients carrying the same NR5A1 variant, indicating that there is no specific genotype-phenotype correlation. Genetic tests are crucial diagnostic tools that should be used early in the diagnostic pathway, as early as the neonatal period, when gonadal dysgenesis is the main manifestation of NR5A1 mutation. NR5A1 gene mutations could be mainly associated with amenorrhea, ovarian failure, hypogonadism, and infertility during puberty. Fertility preservation techniques should be considered as early as possible.

Cryptorchidism and puberty

Cryptorchidism is the condition in which one or both testes have not descended adequately into the scrotum. The congenital form of cryptorchidism is one of the most prevalent urogenital anomalies in male newborns. In the acquired form of cryptorchidism, the testis that was previously descended normally is no longer located in the scrotum. Cryptorchidism is associated with an increased risk of infertility and testicular germ cell tumors. However, data on pubertal progression are less well-established because of the limited number of studies. Here, we aim to review the currently available data on pubertal development in boys with a history of non-syndromic cryptorchidism-both congenital and acquired cryptorchidism. The review is focused on the timing of puberty, physical changes, testicular growth, and endocrine development during puberty. The available evidence demonstrated that the timing of the onset of puberty in boys with a history of congenital cryptorchidism does not differ from that of non-cryptorchid boys. Hypothalamic-pituitary-gonadal hormone measurements showed an impaired function or fewer Sertoli cells and/or germ cells among boys with a history of cryptorchidism, particularly with a history of bilateral cryptorchidism treated with orchiopexy. Leydig cell function is generally not affected in boys with a history of cryptorchidism. Data on pubertal development among boys with acquired cryptorchidism are lacking; therefore, more research is needed to investigate pubertal progression among such boys.

[Hormonal and genetic causes of cryptorchidism]

Cryptorchidism is the most frequent congenital disorders of the reproductive system, is present in 2-3% of term newborn boys. Genes involved in embryonic testicular migration are known but their role in cryptorchidism development are not investigated enough. Genetical causes of cryptorchidism are identified in 5-7% of patients. The article contains data on the role of insulin-like peptide 3 and its receptor, anti-Müllerian hormone, gonadotropins, androgens in embryonic testicular migration. INSL3 and AMH are presented as markers of testicular dysfunction associated with cryptorchidism. Hypogonadotropic hypogonadism is also associated with cryptorchidism and can be diagnosed based on it. Results of modern investigations determine the necessary of hormonal and genetical examination of patients with isolated cryptorchidism to detect causes of cryptorchidism and manage of patients.

Reproductive Markers of Testicular Function and Size During Puberty in Boys With and Without a History of Cryptorchidism

CONTEXT

Longitudinal data on levels of hypothalamic-pituitary-gonadal axis hormones and insulin-like growth factor I (IGF-I) during puberty in boys with a history of cryptorchidism are largely missing.

OBJECTIVE

We aimed to compare pubertal hormone levels between boys with a history of congenital cryptorchidism who experienced spontaneous testicular descent or underwent orchiopexy and boys without a history of cryptorchidism.

METHODS

This was a nested case-control study within a population-based birth cohort, with a prospective, longitudinal pubertal follow-up every 6 months (2005 to 2019). Participants were 109 Finnish boys, including boys with a history of unilateral cryptorchidism who underwent orchiopexy (n = 15), unilateral cryptorchidism who had spontaneous testicular descent (n = 15), bilateral cryptorchidism who underwent orchiopexy (n = 9), bilateral cryptorchidism who had spontaneous testicular descent (n = 7), and controls (n = 63). Serum reproductive hormone levels and testicular volumes were measured.

RESULTS

From around onset of puberty, boys with bilateral cryptorchidism who underwent orchiopexy had significantly higher follicle-stimulating hormone (FSH) and lower inhibin B levels than controls. Boys with unilateral cryptorchidism who underwent orchiopexy had significantly higher FSH than controls, whereas inhibin B levels were similar. Testosterone, luteinizing hormone, insulin-like factor 3, and IGF-I were generally similar between groups. Testicular volume of boys with unilateral or bilateral cryptorchidism who underwent orchiopexy was smaller than that of the controls from 1 year after pubertal onset (P < 0.05).

CONCLUSION

Cryptorchid boys, particularly those with bilateral cryptorchidism who underwent orchiopexy, had altered levels of serum biomarkers of Sertoli cells and germ cells and smaller testicular volumes compared with controls.

Identification of a window of androgen sensitivity for somatic cell function in human fetal testis cultured ex vivo

BACKGROUND

Reduced androgen action during early fetal development has been suggested as the origin of reproductive disorders comprised within the testicular dysgenesis syndrome (TDS). This hypothesis has been supported by studies in rats demonstrating that normal male development and adult reproductive function depend on sufficient androgen exposure during a sensitive fetal period, called the masculinization programming window (MPW). The main aim of this study was therefore to examine the effects of manipulating androgen production during different timepoints during early human fetal testis development to identify the existence and timing of a possible window of androgen sensitivity resembling the MPW in rats.

METHODS

The effects of experimentally reduced androgen exposure during different periods of human fetal testis development and function were examined using an established and validated human ex vivo tissue culture model. The androgen production was reduced by treatment with ketoconazole and validated by treatment with flutamide which blocks the androgen receptor. Testicular hormone production ex vivo was measured by liquid chromatography-tandem mass spectrometry or ELISA assays, and selected protein markers were assessed by immunohistochemistry.

RESULTS

Ketoconazole reduced androgen production in testes from gestational weeks (GW) 7-21, which were subsequently divided into four age groups: GW 7-10, 10-12, 12-16 and 16-21. Additionally, reduced secretion of testicular hormones INSL3, AMH and Inhibin B was observed, but only in the age groups GW 7-10 and 10-12, while a decrease in the total density of germ cells and OCT4⁺ gonocytes was found in the GW 7-10 age group. Flutamide treatment in specimens aged GW 7-12 did not alter androgen production, but the secretion of INSL3, AMH and Inhibin B was reduced, and a reduced number of pre-spermatogonia was observed.

CONCLUSIONS

This study showed that reduced androgen action during early development affects the function and density of several cell types in the human fetal testis, with similar effects observed after ketoconazole and flutamide treatment. The effects were only observed within the GW 7-14 period-thereby indicating the presence of a window of androgen sensitivity in the human fetal testis.

Cryptorchidism: The dog as a study model

Cryptorchidism (CO) or undescended testicle is an abnormality of male gonadal development that can generate long-term repercussions in men, such as infertility and germ cell neoplasia in situ (GCNIS). The origin of these alterations in humans is not completely clear, due to the absence of an animal model with similar testicular development as in humans with CO. This work intends to describe the testicular histological development of dogs with congenital CO, and determine whether the species could adequately serve as a study model for this pathology in humans. The study was carried out with 36 dogs, equally distributed in two groups: healthy control (CTRL) and CO groups. The contralateral testis to the undescended one in CO group of the animals was considered and analyzed. Each group was subdivided in three stages of development: (1) peripubertal stage (6–8 months), (2) young adult (9–48 months) and (3) senile (49–130 months). Histological development, the presence of cells with gonocyte morphology, cell proliferation, testicular lipoperoxidation and hormonal concentrations of testosterone, estradiol, FSH and LH were evaluated and described. In the cryptorchid testes, the first histological alterations appeared from the first stage of development and were maintained until the senile stage. A pronounced testicular lipoperoxidation occurred only in the second stage of development. The histological alterations due to CO were markedly evident in the young adult stage. Testosterone concentrations witnessed a decrease starting from in the second stage and kept on until the last stage. The contralateral testes of the CO animals showed alterations that positioned them between the control and CO testes. Testicular development of dogs with CO is similar to that of humans. The results of the study suggest that this species could serve as a suitable model for the study of CO in humans.

Potential Impact of mini-puberty on fertility

Mini-puberty is defined as the period in infancy with elevated FSH and LH resulting increased levels of sex hormones. It differs between boys and girls. Its impact on future fertility is largely unknown. This mini-review focus on the effects of mini-puberty on genital development and some aspects possibly related to future fertility.

Deciphering Sex-Specific Differentiation of Human Fetal Gonads: Insight From Experimental Models

Sex-specific gonadal differentiation is initiated by the expression of SRY in male foetuses. This promotes a signalling pathway directing testicular development, while in female foetuses the absence of SRY and expression of pro-ovarian factors promote ovarian development. Importantly, in addition to the initiation of a sex-specific signalling cascade the opposite pathway is simultaneously inhibited. The somatic cell populations within the gonads dictates this differentiation as well as the development of secondary sex characteristics via secretion of endocrine factors and steroid hormones. Opposing pathways SOX9/FGF9 (testis) and WNT4/RSPO1 (ovary) controls the development and differentiation of the bipotential mouse gonad and even though sex-specific gonadal differentiation is largely considered to be conserved between mice and humans, recent studies have identified several differences. Hence, the signalling pathways promoting early mouse gonad differentiation cannot be directly transferred to human development thus highlighting the importance of also examining this signalling in human fetal gonads. This review focus on the current understanding of regulatory mechanisms governing human gonadal sex differentiation by combining knowledge of these processes from studies in mice, information from patients with differences of sex development and insight from manipulation of selected signalling pathways in ex vivo culture models of human fetal gonads.

Dynamic Changes of Reproductive Hormones in Male Minipuberty: Temporal Dissociation of Leydig and Sertoli Cell Activity

CONTEXT

The male hypothalamic-pituitary-gonadal (HPG) axis is transiently active during the first months of life with surging serum concentrations of reproductive hormones. This period, termed minipuberty, appears to be essential for priming testicular function. Despite the central role for male reproductive function, longitudinal data on HPG axis activation in infancy is sparse.

OBJECTIVE

To explore the dynamics of HPG hormone activity in healthy male infants, to assess the association of HPG axis activity and testicular volume, and to establish reference curves for serum levels of reproductive hormones.

DESIGN

Prospective, longitudinal birth cohort (the COPENHAGEN Minipuberty Study, 2016-2018, 1-year follow-up).

SETTING

Population-based.

PATIENTS OR OTHER PARTICIPANTS

Healthy, male, term, singleton newborns were followed from birth on with repeated clinical examinations including blood sampling during a 1-year follow-up. A total of 128 boys contributed to this study, while 119 participated in the postnatal follow-up.

MAIN OUTCOME MEASURES

Serum reproductive hormone concentrations and testicular volume.

RESULTS

Reproductive hormone concentrations showed marked dynamics during the first 6 months of age. Gonadotropins, total testosterone, and insulin-like factor 3 peaked at around 1 month of age. Inhibin B, anti-Müllerian hormone, and testicular volume peaked at around 4 to 5 months. Correlations largely recapitulated typical HPG axis pathways but also differed significantly from adult men.

CONCLUSIONS

We demonstrate a temporal dissociation of Leydig and Sertoli cell activity during male minipuberty and provide reference curves for reproductive hormones.

Expression and Role of INSL3 in the Fetal Testis

Insulin-like peptide 3 (INSL3) is a small peptide hormone of the insulin-relaxin family which is produced and secreted by the fetal Leydig cells in the testes only. It appears to be undetectable in female fetuses. In the human fetus INSL3 synthesis begins immediately following gonadal sex determination at weeks 7 to 8 post coitum and the peptide can be detected in amniotic fluid 1 to 2 weeks later. INSL3 acts through a unique G-protein-coupled receptor, called RelaXin-like Family Peptide receptor 2 (RXFP2), which is expressed by the mesenchymal cells of the gubernacular ligament linking the testes to the inguinal wall. The role of INSL3 in the male fetus is to cause a thickening of the gubernaculum which then retains the testes in the inguinal region, while the remainder of the abdominal organs grow away in an antero-dorsal direction. This represents the first phase of testis descent and is followed later in pregnancy by the second inguino-scrotal phase whereby the testes pass into the scrotum through the inguinal canal. INSL3 acts as a significant biomarker for Leydig cell differentiation in the fetus and may be reduced by maternal exposure to endocrine disrupting chemicals, such as xenoestrogens or phthalates, leading to cryptorchidism. INSL3 may have other roles within the fetus, but as a Leydig cell biomarker its reduction acts also as a surrogate for anti-androgen action.

Insulin-like peptide 3 in domestic animals with normal and abnormal reproductive functions, in comparison to rodents and humans

Background

Insulin-like peptide 3 (INSL3) is a circulating hormone secreted from only testis and ovaries in mammals. Findings on INSL3 have been gathered from subjects with normal and abnormal reproductive statuses, especially rodents and humans. However, little to no review articles focusing on INSL3 in domestic animals exist.

Methods

The author reviewed the past and recent literature regarding the structure, expression, roles of INSL3 in the reproductive organs, and its circulation under normal and aberrant reproductive conditions in domestic animals in comparison with rodents and humans.

Main findings

As with humans and rodents, blood INSL3 concentrations rise around puberty in normal male domestic animals and are associated with testicular size. INSL3 levels are acutely upregulated by luteinizing hormone (LH), and the increase is smaller than that of testosterone in male ruminants, whereas the acute regulation of INSL3 by LH does not occur in human men. Dogs with cryptorchidism and bulls with abnormal semen have lowered INSL3 levels.

Conclusion

The findings regarding INSL3 secretions in male domestic animals with normal and aberrant reproductive functions illustrate similar or dissimilar points to humans and rodents. Data on blood INSL3 levels in normal and abnormal female domestic species are still limited and require further investigation.

Insulin-like peptide 3 (INSL3) in congenital hypogonadotrophic hypogonadism (CHH) in boys with delayed puberty and adult men

BACKGROUND

Delayed puberty in males is almost invariably associated with constitutional delay of growth and puberty (CDGP) or congenital hypogonadotrophic hypogonadism (CHH). Establishing the cause at presentation is challenging, with "red flag" features of CHH commonly overlooked. Thus, several markers have been evaluated in both the basal state or after stimulation e.g. with gonadotrophin releasing hormone agonist (GnRHa).Insulin-like peptide 3 (INSL3) is a constitutive secretory product of Leydig cells and thus a possible candidate marker, but there have been limited data examining its role in distinguishing CDGP from CHH. In this manuscript, we assess INSL3 and inhibin B (INB) in two cohorts: 1. Adolescent boys with delayed puberty due to CDGP or CHH and 2. Adult men, both eugonadal and having CHH.

MATERIALS AND METHODS

Retrospective cohort studies of 60 boys with CDGP or CHH, as well as 44 adult men who were either eugonadal or had CHH, in whom INSL3, INB, testosterone and gonadotrophins were measured. Cohort 1: Boys with delayed puberty aged 13-17 years (51 with CDGP and 9 with CHH) who had GnRHa stimulation (subcutaneous triptorelin 100mcg), previously reported with respect to INB. Cohort 2: Adult cohort of 44 men (22 eugonadal men and 22 men with CHH), previously reported with respect to gonadotrophin responses to kisspeptin-54.

RESULTS

Median INSL3 was higher in boys with CDGP than CHH (0.35 vs 0.15 ng/ml; p=0.0002). Similarly, in adult men, median INSL3 was higher in eugonadal men than CHH (1.08 vs 0.05 ng/ml; p<0.0001). However, INSL3 more accurately differentiated CHH in adult men than in boys with delayed puberty (auROC with 95% CI in adult men: 100%, 100-100%; boys with delayed puberty: 86.7%, 77.7-95.7%).Median INB was higher in boys with CDGP than CHH (182 vs 59 pg/ml; p<0.0001). Likewise, in adult men, median INB was higher in eugonadal men than CHH (170 vs 36.5 pg/ml; p<0.0001). INB performed better than INSL3 in differentiating CHH in boys with delayed puberty (auROC 98.5%, 95.9-100%), than in adult men (auROC 93.9%, 87.2-100%).

CONCLUSION

INSL3 better identifies CHH in adult men, whereas INB better identifies CHH in boys with delayed puberty.

Genetics of cryptorchidism and testicular regression

Cryptorchidism, i.e., undescended testis, is one of the most common genital malformations in newborn male babies. The birth rate of cryptorchidism varies from 1.6 to 9.0 %. Etiology of disrupted testicular descent is complex and predisposing causes include genetic, hormonal, environmental, lifestyle and maternal factors. Testicular descent occurs in two major steps and testicular hormones and normal function of hypothalamic-pituitary-testicular axis are important for normal descent. Several gene mutations are associated with syndromic cryptorchidism but they are rarely found in boys with isolated undescended testis. Testicular regression can also cause an empty scrotum. Normal male genital phenotype indicates that the boy has had functioning testis during development. Torsion of the testis can cause testicular regression but in many cases the reason for vanishing testis remains elusive. In this narrative review we discuss genetics of cryptorchidism and testicular regression.

Morphometric study of the testis in sheep embryos using unbiased design-based stereology

Sheep have been used as translational models of human postnatal testicular development. However, the morphometric features of the normal developing testis in sheep embryos have not been previously investigated using stereology. The objective of the present work was to establish normal quantitative parameters for fetal testicular tissue components in sheep, using unbiased design-based stereological methods. Twenty-four sheep embryos were divided into four gestational age groups (9-11, 12-14, 15-17 and 18-20 weeks of gestation) on the basis of the embryos' crown-rump length. Isotropic, systematic uniform random sections of the left testes were obtained by employing the orientator method. Testicular total volume, the absolute and proportional volumes occupied by the seminiferous tubules and interstitial tissue, as well as the seminiferous tubule length, were estimated using the point-counting system and the unbiased counting frame principle. All the parameters, with the exception of the interstitial tissue's fractional volume, gradually increased along with gestational age, with the maximum increase especially seen in the late fetal stages. The proportional volume of the interstitial tissue, on the other hand, showed a decreasing trend along with increasing gestational age. The absolute volume of the testes, of the seminiferous tubules and of the interstitial tissue, and the length of the seminiferous tubules showed a significant (p< 0.05) positive linear correlation with gestational age. Several similarities were observed with human testicular embryogenesis. The stereological data emerging from the present study might prove useful as basic contribution to the fields of andrology and embryology and stimulate further research in these areas.

Congenital hypogonadotropic hypogonadism: from clinical characteristics to genetic aspects

Congenital hypogonadotropic hypogonadism (CHH) is a rare disorder caused by a deficiency in gonadotropin-releasing hormone (GnRH). CHH is characterized by delayed puberty and/or infertility; this is because GnRH is the main component of the hypothalamic-pituitary-gonadal (HPG) axis, which is a key factor in pubertal development and reproductive function completion. However, since the development of sexual characteristics and reproduction begins in the prenatal period and is very complex and delicate, the clinical characteristics and involved genes are very diverse. In particular, the HPG axis is activated three times in a lifetime, and the symptoms and biochemical findings of CHH vary by period. In addition, related genes also vary according to the formation and activation process of the HPG axis. In this review, the clinical characteristics and treatment of CHH according to HPG axis activation and different developmental periods are reviewed, and the related genes are summarized according to their pathological mechanisms.

Scrotal base distance

Background:

Anogenital distance (AGD) in both humans and animals is a known reflection of fetal endocrine effect on genital virilization and the related abnormalities, including cryptorchidism and hypospadias. However, we introduce here and investigate scrotal base distance (SBD) as a sensitive genital anthropometric biomarker in human infants with cryptorchidism and hypospadias, which are considered early manifestations of testicular dysgenesis syndrome. We aim to assess SBD in patients with cryptorchidism or hypospadias against healthy subjects.

Material and methods:

Patients with hypospadias (n = 61, age 17.4 ± 6.3 months) or cryptorchidism (n = 51, age 11.4 ± 4.8 months) were enrolled for assessment of SBD, AGD, and penile length; and compared with a cohort of 102 full-term healthy boys for standard ritual circumcision by measuring age-specific standard deviation scores.

Results:

Patients having hypospadias had lower mean SBD, AGD, and penile length standard deviation scores than the control group (p < 0.01). These values in patients with cryptorchidism were longer than mean values in boys with hypospadias (p < 0.01) and shorter than mean values in the control group.

Conclusions:

We showed that SBD, AGD, and penile length were lower in patients with cryptorchidism or hypospadias compared to normative data measured from a control group of healthy boys for ritual circumcision. These results enforce the use of SBD as an objective anthropometric measurement and a viable biomarker to assess the effects of fetal endocrine imbalance on male external genitalia development.

Serum insulin-like factor 3 quantification by LC-MS/MS in male patients with hypogonadotropic hypogonadism and Klinefelter syndrome

PURPOSE

Insulin-like factor 3 (INSL3) is an emerging testicular marker, yet larger studies elucidating the clinical role of INSL3 in patients with hypogonadism are lacking. The aim was to describe serum INSL3 concentrations analyzed by LC-MS/MS methodology in males with hypogonadotropic hypogonadism (HH) and Klinefelter syndrome (KS).

METHODS

This was a combined study from two tertiary centers in Denmark and France analyzing INSL3 concentrations by LC-MS/MS. In total, 103 patients with HH and 82 patients with KS were grouped into treated (HH: n = 96; KS: n = 71) or untreated (HH: n = 7; KS: n = 11). Treatment modalities included testosterone and hCG. Serum concentrations and standard deviation (SD) scores of INSL3, total testosterone, and LH according to age and treatment were evaluated.

RESULTS

In both HH and KS, INSL3 concentrations were low. In HH, INSL3 was low regardless of treatment, except for some hCG-treated patients with normal concentrations. In untreated HH, testosterone was low, while normal to high in most testosterone- and hCG-treated patients. In untreated KS, INSL3 and testosterone concentrations were low to normal, while in testosterone-treated KS, serum INSL3 was low in most patients. INSL3 SD scores were significantly lower in untreated HH than in untreated KS (p = 0.01).

CONCLUSIONS

The dichotomy between lower INSL3 and higher testosterone concentrations, particularly observed in hCG-treated patients with HH, confirms that INSL3 is a different marker of Leydig cell function than testosterone. However, the clinical application of INSL3 in males with hypogonadism remains unclear.

Diverse functions of insulin-like 3 peptide

Insulin-like 3 peptide (INSL3) is a member of the insulin-like peptide superfamily and is the only known physiological ligand of relaxin family peptide receptor 2 (RXFP2), a G protein-coupled receptor (GPCR). In mammals, INSL3 is primarily produced both in testicular Leydig cells and in ovarian theca cells, but circulating levels of the hormone are much higher in males than in females. The INSL3/RXFP2 system has an essential role in the development of the gubernaculum for the initial transabdominal descent of the testis and in maintaining proper reproductive health in men. Although its function in female physiology has been less well-characterized, it was reported that INSL3 deletion affects antral follicle development during the follicular phase of the menstrual cycle and uterus function. Since the discovery of its role in the reproductive system, the study of INSL3/RXFP2 has expanded to others organs, such as skeletal muscle, bone, kidney, thyroid, brain, and eye. This review aims to summarize the various advances in understanding the physiological function of this ligand-receptor pair since its first discovery and elucidate its future therapeutic potential in the management of various diseases.

Correlation between insulin-like peptide 3 and appendix testis length in congenital cryptorchidism

AIM

The appendix testis (AT) is a vestigial remnant of Müller's paramesonephric duct. Insulin-like 3 hormone (INSL3) is produced in the Leydig cells of the testis. We investigated the possible correlation between AT length and plasma INSL3 concentrations in patients with congenital cryptorchidism (CCO) and patients with hydrocele, who served as controls.

METHODS

A total of 40 patients with CCO and 34 patients with hydrocele and orthotopic testes were investigated. Sixteen patients presented high cryptorchidism and 24 low cryptorchidism. During surgery, AT was identified in 34 patients with CCO (high cryptorchidism:15, low cryptorchidism:19) and 28 controls. Plasma INSL3 levels were measured with a spectrophotometry enzyme immunoassay Elisa sandwich technique.

RESULTS

AT was present in 85.0% of the boys with CCO and 82.4% of the controls. A significant positive correlation was found between the AT length and INSL3 concentrations in CCO patients.

CONCLUSIONS

A longer AT may reflect better testicular function in boys with CCO, since it is correlated with higher INSL3 concentrations.

A history of cryptorchidism is associated with impaired testicular function in early adulthood: a cross-sectional study of 6376 men from the general population

STUDY QUESTION

Is there a difference in testicular function in early adulthood between men born with cryptorchidism and men born with normally descended testes?

SUMMARY ANSWER

In men from the general population, a history of cryptorchidism was associated with lower total testis volume and impaired semen quality as well as altered serum levels of reproductive hormones.

WHAT IS KNOWN ALREADY

The association between cryptorchidism and testicular function is well documented in studies based on sub-fertile or infertile men recruited from a clinical setting. However, the association has not previously been investigated in men from the general population, who were unselected regarding fertility status.

STUDY DESIGN, SIZE, DURATION

This is a cross-sectional population-based study of 6376 young Danish men examined from 1996 to 2017.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study is based on young men from the greater Copenhagen area, Denmark (median age of 19 years) who were unselected regarding fertility status and semen quality. The young men delivered a semen sample, had a blood sample drawn and underwent a physical examination including assessment of testis volume. Participants completed a questionnaire regarding cryptorchidism at birth, current lifestyle and their mother’s pregnancy, after consulting their mother. The differences in markers of testicular function, including testis volume, semen parameters and reproductive hormones between men with and without a history of cryptorchidism were investigated with multiple linear regression analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

The participation rate was 24% for the entire study period. Overall, a history of cryptorchidism was associated with reduced testicular function. In the adjusted models, a history of cryptorchidism was associated with a 3.5 ml lower total testis volume, determined by orchidometer (P &lt; 0.001), 28% lower sperm concentration (95% CI: −37 to −20) and 26% lower inhibin B/FSH ratio (95% CI: −50 to −22) compared to men without a history of cryptorchidism, suggesting a reduced spermatogenetic capacity. Men with a history of cryptorchidism also had a slightly reduced Leydig cell function expressed as a 6% lower testosterone/LH ratio (95% CI: −12 to −0.7). The significant effect sizes and different markers of testicular function pointing in the same direction across the different models based on a large sample size support that the results are not chance findings.

LIMITATIONS, REASONS FOR CAUTION

Information on cryptorchidism at birth and treatment modus was obtained by retrospective self-report, and each participant only delivered one semen sample.

WIDER IMPLICATIONS OF THE FINDINGS

The results suggest that men with a history of cryptorchidism could be at increased risk of experiencing fertility problems. However, among these men there is a wide variation in semen quality and further research is needed in order to identify the subgroup of boys born with cryptorchidism who are at the greatest risk of impaired semen quality when reaching adulthood.

STUDY FUNDING/COMPETING INTEREST(S)

The study received financial support from the Research fund of Rigshospitalet, Copenhagen University Hospital; the European Union (Contract numbers BMH4-CT96-0314, QLK4-CT-1999-01422, QLK4-CT-2002-00603. FP7/2007-2013, DEER Grant agreement no. 212844); the Danish Ministry of Health; the Danish Environmental Protection Agency; A.P. Møller and wife Chastine McKinney Møllers Foundation; and Svend Andersens Foundation. None of the founders had any role in the study design, collection, analysis or interpretation of data, writing of the paper or publication decisions. The authors have nothing to declare.

TRIAL REGISTRATION NUMBER

N/A.

Minipuberty in Klinefelter syndrome: Current status and future directions

Klinefelter syndrome is highly underdiagnosed and diagnosis is often delayed. With the introduction of non-invasive prenatal screening, the diagnostic pattern will require an updated description of the clinical and biochemical presentation of infants with Klinefelter syndrome. In the first months of life, the hypothalamic-pituitary-gonadal (HPG)-axis is transiently activated in healthy males during the so-called minipuberty. This period represents a "window of opportunity" for evaluation of the HPG-axis before puberty and without stimulation tests. Infants with Klinefelter syndrome present with a hormonal surge during the minipuberty. However, only a limited number of studies exist, and the results are contradictory. Further studies are needed to clarify whether infants with Klinefelter syndrome present with impaired testosterone production during the minipuberty. The aim of this review is to describe the clinical and biochemical characteristics of the neonate and infant with Klinefelter syndrome with special focus on the minipuberty and to update the clinical recommendations for Klinefelter syndrome during infancy.

Minipuberty of human infancy - A window of opportunity to evaluate hypogonadism and differences of sex development?

Activation of the hypothalamic-pituitary-gonadal (HPG) axis happens in 3 phases during life. The first phase is during fetal life and is only separated from the second phase, called minipuberty, by the high concentration of placental hormones at birth. The third period of activation of the HPG axis is puberty and is well-described. Minipuberty consists of the neonatal activation of the HPG axis, mainly in the first 1-6 months, where the resulting high levels of gonadotropins and sex steroids induce the maturation of sexual organs in both sexes. With gonadal activation, testosterone levels rise in boys with peak levels after 1-3 months, which results in penile and testicular growth. In girls, gonadal activation leads to follicular maturation and a fluctuating increase in estrogen levels, with more controversy regarding the actual influence on the target tissue. The regulation of the HPG axis is complex, involving many biological and environmental factors. Only a few of these have known effects. Many details of this complex interaction of factors remain to be elucidated in order to understand the mechanisms underlying the first postnatal activation of the HPG axis as well as mechanisms shutting down the HPG axis, resulting in the hormonal quiescence observed between minipuberty and puberty. Minipuberty allows for the maturation of sexual organs and forms a platform for future fertility, but the long-term significance is still not absolutely clear. However, it provides a window of opportunity in the early detection of differences of sexual development, offering the possibility of initiating early medical treatment in some cases.

Male Hypogonadism and Disorders of Sex Development

Disorders of Sex Development (DSD) are congenital anomalies in which there is a discordance between chromosomal, genetic, gonadal, and/or internal/external genital sex. In XY individuals, the process of fetal sex differentiation can be disrupted at the stage of gonadal differentiation, resulting in gonadal dysgenesis, a form of early fetal-onset primary hypogonadism characterized by insufficient androgen and anti-Müllerian hormone (AMH) production, which leads to the development of ambiguous or female genitalia. The process of sex differentiation can also be disrupted at the stage of genital differentiation, due to isolated defects in androgen or AMH secretion, but not both. These are forms of fetal-onset hypogonadism with dissociated gonadal dysfunction. In this review, we present a perspective on impaired testicular endocrine function, i.e., fetal-onset male hypogonadism, resulting in incomplete virilization at birth.

Ontogeny of Hypothalamus-Pituitary Gonadal Axis and Minipuberty: An Ongoing Debate?

The fetal hypothalamus-pituitary gonadal (HPG) axis begins to function during mid-gestation but its activity decreases during late pregnancy due to the suppressive effects of placental estrogens. Placental hormones drop immediately after birth, FSH and LH surge at around 1 week and peak between 1 and 3 months of life. The HPG axis is activated in both sexes, but a sexual dimorphism is evident with higher LH values in boys, while FSH prevails in girls. Both gonadotrophins decline in boys by around 6 months of age. In girls, LH declines at the same time as in boys, while FSH persists elevated up to 3 or 4 years of age. As a result of gonadotropin activation, testicular testosterone increases in males and ovarian estradiol rises in females. These events clinically translate into testicular and penile growth in boys, enlargement of uterus and breasts in girls. The functional impact of HPG axis activity in infancy on later reproductive function is uncertain. According to the perinatal programming theory, this period may represent an essential programming process. In boys, long-term testicular hormonal function and spermatogenesis seem to be, at least in part, regulated by minipuberty. On the contrary, the role of minipuberty in girls is still uncertain. Recently, androgen exposure during minipuberty has been correlated with later sex-typed behavior. Premature and/or SGA infants show significant differences in postnatal HPG axis activity in comparison to full-term infants and the consequences of these differences on later health and disease require further research. The sex-dimorphic HPG activation during mid-gestation is probably responsible for the body composition differences observed ad birth between boys and girls, with boys showing greater total body mass and lean mass, and a lower proportion of fat mass. Testosterone exposure during minipuberty further contributes to these differences and seems to be responsible for the significantly higher growth velocity observed in male infants. Lastly, minipuberty is a valuable "window of opportunity" for differential diagnosis of disorders of sex development and it represents the only time window before puberty when congenital hypogonadism can be diagnosed by the simple analysis of basal gonadotropin and gonadal hormone levels.

Hypogonadism in Pediatric Health: Adult Medicine Concepts Fail

The classical definition of hypogonadism, used in adult medicine, as gonadal failure resulting in deficient steroid and gamete production, and its classification into hypergonadotropic and hypogonadotropic refer to primary gonadal and hypothalamic-pituitary disorders respectively and may lead to under- or misdiagnosis in pediatrics. Indeed, in children with primary gonadal failure, gonadotropin levels may be within the reference range for age. Conversely, since gonadotropins and steroids are normally low during childhood, it may prove impossible to show the existence of a hypogonadotropic state before pubertal age. Anti-Müllerian hormone (AMH) and inhibin B arise as more adequate biomarkers to assess gonadal function and increase the possibility of making an earlier diagnosis of hypogonadism in children, which may positively impact on timely management.

Testis Development

Production of sperm and androgens is the main function of the testis. This depends on normal development of both testicular somatic cells and germ cells. A genetic program initiated from the Y chromosome gene sex-determining region Y (SRY) directs somatic cell specification to Sertoli cells that orchestrate further development. They first guide fetal germ cell differentiation toward spermatogenic destiny and then take care of the full service to spermatogenic cells during spermatogenesis. The number of Sertoli cells sets the limits of sperm production. Leydig cells secrete androgens that determine masculine development. Testis development does not depend on germ cells; that is, testicular somatic cells also develop in the absence of germ cells, and the testis can produce testosterone normally to induce full masculinization in these men. In contrast, spermatogenic cell development is totally dependent on somatic cells. We herein review germ cell differentiation from primordial germ cells to spermatogonia and development of the supporting somatic cells. Testicular descent to scrota is necessary for normal spermatogenesis, and cryptorchidism is the most common male birth defect. This is a mild form of a disorder of sex differentiation. Multiple genetic reasons for more severe forms of disorders of sex differentiation have been revealed during the last decades, and these are described along with the description of molecular regulation of testis development.

Anogenital distance is associated with genital measures and seminal parameters but not anthropometrics in a large cohort of young adult men

STUDY QUESTION

Is the anogenital distance (AGD) correlated to anthropometric, genital and sperm parameters in young adult men?

SUMMARY ANSWER

We observed that reduced AGD is strongly associated with altered semen parameters and reduced testicular volume.

WHAT IS KNOWN ALREADY

Abnormalities in the foetal development of the testis have been suggested as causative of common male reproductive disorders, such as cryptorchidism, hypospadias, reduced semen quality and testicular germ cell tumour, collectively defined as 'testicular dysgenesis syndrome'. In human epidemiological studies, alterations in AGD have been frequently associated with clinically relevant outcomes of reproductive health, suggesting AGD as a marker of foetal testicular development.

STUDY DESIGN, SIZE, DURATION

This study was performed within the annual screening protocol to evaluate male reproductive health in the high schools of Padua and surroundings (Veneto Region, the North-East of Italy). Here we report the findings of 794 subjects who completed the study protocol between October 2016 and May 2017.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We evaluated 794 students aged 18-19 years recording the following parameters: height, weight, BMI, waist circumference, arm span, pubis-to-floor and crown-to-pubis length, penile length and circumference, testicular volumes, semen parameters and AGD (measured from the posterior base of the scrotum to the centre of the anus).

MAIN RESULTS AND THE ROLE OF CHANCE

Of the subjects, 49% had an abnormal arm span-height difference (>3 cm) and 63.4% had an altered ratio of crown-to-pubis/pubis-to-floor length (≤0.92). The rate of subjects with reduced testicular volume was 23%. Median sperm concentration was 51.0× 106/ml and total sperm count was 122.5 × 106. AGD showed a direct positive relation with testicular volume and penile length and circumference (R = 0.265, 0.176 and 0.095, respectively, all P < 0.05). No significant relation was observed between AGD and anthropometric parameters. Sperm concentration, total sperm count, progressive motility and normal morphology showed a significant and positive correlation with AGD (R = 0.205, 0.210, 0.216 and 0.117, respectively, all P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

Our cohort of young adults is not representative of the general population. Hormonal evaluation was missing.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings show that AGD is associated with testicular volumes, penile measures and seminal parameters in young adult men. Because AGD is hormonally determined during foetal life, the reported high incidence of reduced semen quality and reduced testicular volume could be related to a reduced androgenic exposure in utero. AGD could represent a simple and useful method to evaluate testicular and penile development in adult men.

STUDY FUNDING/COMPETING INTEREST(S)

The authors have no potential conflict of interest to declare. No external funding was obtained for this study.

TRIAL REGISTRATION NUMBER

N/A.

INSL3 in the muscolo-skeletal system

Bone and skeletal muscle are currently considered a unified functional unit, showing complementary regulation at mechanical, biochemical, paracrine and metabolic levels. This functional unit undergoes a central hormonal regulation which is mainly ascribed to sex steroids and, in particular, androgens. However, recent evidence suggest that another testicular hormone lines the classical anabolic effect of testosterone on bone and muscle, the insulin-like peptide 3 (INSL3) acting on its specific receptor RXFP2. This minireview focuses on the most recent findings describing the role of INSL3/RXFP2 axis on the muscolo-skeletal system, from the mechanistic insights to the phenotypic consequences. Pathophysiological and therapeutic widenings deriving from available data are also discussed.

Postnatal Testicular Activity in Healthy Boys and Boys With Cryptorchidism

Cryptorchidism, or undescended testis, is a well-known risk factor for testicular cancer and impaired semen quality in adulthood, conditions which have their origins in early fetal and postnatal life. In human pregnancy, the interplay of testicular and placental hormones as well as local regulatory factors and control by the hypothalamic-pituitary (HP) axis, lead to testicular descent by term. The normal masculine development may be disrupted by environmental factors or genetic defects and result in undescended testes. Minipuberty refers to the postnatal re-activation of the HP-testicular (T) axis after birth. During the first weeks of life, gonadotropin levels increase, followed by activation and proliferation of testicular Leydig, Sertoli and germ cells. Consequent rise in testosterone levels results in penile growth during the first months of life. Testicular size increases and testicular descent continues until three to five months of age. Insufficient HPT axis activation (e.g., hypogonadotropic hypogonadism) is often associated with undescended testis and therefore minipuberty is considered an important phase in the normal male reproductive development. Minipuberty provides a unique window of opportunity for the early evaluation of HPT axis function during early infancy. For cryptorchid boys, hormonal evaluation during minipuberty may give a hint of the underlying etiology and aid in the evaluation of the later risk of HPT axis dysfunction and impaired fertility. The aim of this review is to summarize the current knowledge of the role of minipuberty in testicular development and descent.

Insulin-Like Peptide 3 (INSL3) Serum Concentration During Human Male Fetal Life

Context: Insulin-like peptide 3 (INSL3), a protein hormone produced by Leydig cells, may play a crucial role in testicular descent as male INSL3 knockout mice have bilateral cryptorchidism. Previous studies have measured human fetal INSL3 levels in amniotic fluid only. Objective: To measure INSL3 serum levels and mRNA in fetal umbilical cord blood and fetal testes, respectively. Design: INSL3 concentrations were assayed on 50 μl of serum from male human fetal umbilical cord blood by a non-commercial highly sensitive and specific radioimmunoassay. For secondary confirmation, quantitative real-time PCR was used to measure INSL3 relative mRNA expression in 7 age-matched human fetal testes. Setting: UT Southwestern Medical Center, Dallas, TX and Medical University of South Carolina, Charleston, SC. Patients or other Participants: Twelve human male umbilical cord blood samples and 7 human male testes were obtained from fetuses 14-21 weeks gestation. Male sex was verified by leukocyte genomic DNA SRY PCR. Interventions: None. Main Outcome Measures: Human male fetal INSL3 cord blood serum concentrations and testicular relative mRNA expression. Results: INSL3 serum concentrations during human male gestational weeks 15-20 were 2-4 times higher than published prepubertal male levels and were 5-100 times higher than previous reports of INSL3 concentrations obtained from amniotic fluid. Testicular fetal INSL3 mRNA relative expression was low from weeks 14-16, rose significantly weeks 17 and 18, and returned to low levels at week 21. Conclusions: These findings further support the role of INSL3 in human testicular descent and could prove relevant in uncovering the pathophysiology of cryptorchidism.

Hypogonadism and Cryptorchidism

Congenital cryptorchidism (undescended testis) is one of the most common congenital urogenital malformations in boys. Prevalence of cryptorchidism at birth among boys born with normal birth weight ranges from 1.8 to 8.4%. Cryptorchidism is associated with a risk of low semen quality and an increased risk of testicular germ cell tumors. Testicular hormones, androgens and insulin-like peptide 3 (INSL3), have an essential role in the process of testicular descent from intra-abdominal position into the scrotum in fetal life. This explains the increased prevalence of cryptorchidism among boys with diseases or syndromes associated with congenitally decreased secretion or action of androgens, such as patients with congenital hypogonadism and partial androgen insensitivity syndrome. There is evidence to support that cryptorchidism is associated with decreased testicular hormone production later in life. It has been shown that cryptorchidism impairs long-term Sertoli cell function, but may also affect Leydig cells. Germ cell loss taking place in the cryptorchid testis is proportional to the duration of the condition, and therefore early orchiopexy to bring the testis into the scrotum is the standard treatment. However, the evidence for benefits of early orchiopexy for testicular endocrine function is controversial. The hormonal treatments using human chorionic gonadotropin (hCG) or gonadotropin-releasing hormone (GnRH) to induce testicular descent have low success rates, and therefore they are not recommended by the current guidelines for management of cryptorchidism. However, more research is needed to assess the effects of hormonal treatments during infancy on future male reproductive health.

Effects of Osteocalcin on Synthesis of Testosterone and INSL3 during Adult Leydig Cell Differentiation

Proliferation and differentiation of adult Leydig cells are mainly completed in puberty. In many studies, apart from normal postnatal development process, it is widely indicated that, through administrating EDS, Leydig cell population is eliminated and regenerated. It is believed that osteocalcin released from osteoblasts, which is responsible for modulating bone metabolism, induces testosterone production in Leydig cells, independent of the HPG axis. In addition, INSL3 produced by Leydig cells, such as testosterone, plays a critical role in bone metabolism and is known to reflect the development process and functional capacities of Leydig cells. This study is aimed at investigating OC-mediated testosterone regulation and INSL3 synthesis during differentiation of adult Leydig cells that are independent of LH. For this purpose, male rats were divided into 2 groups: prepubertal normal rats and adult EDS-injected rats. Each group was divided into 4 subgroups in which GnRH antagonist or OC was applied. After adult Leydig cells completed their development, testicular tissue samples obtained from the sacrificed rats were examined by light-electron microscopic, immunohistochemical, and biochemical methods. Slight upregulation in 3βHSD, INSL3, and GPRC6A expressions along with the increase in serum testosterone levels was observed in groups treated with osteocalcin against GnRH antagonist. In addition, biochemical and microscopic findings in osteocalcin treated groups were similar to those in control groups. While there was no significant difference in the number of Leydig cells reported, the presence of a significant upregulation in INSL3 and GPRC6A expressions and the increase in serum testosterone and ucOC levels were observed. After evaluation of findings altogether, it is put forward that, for the first time in this study, although osteocalcin treatment made no significant difference in the number of Leydig cells, it increased the level of testosterone through improving the function of existing adult Leydig cells during normal postnatal development process and post-EDS regeneration. This positive correlation between osteocalcin-testosterone and osteocalcin-INSL3 is concluded to be independent of LH at in vivo conditions.

Management of hypogonadism from birth to adolescence

Management of patients with hypogonadism is dependent on the underlying cause. Whilst functional hypogonadism presenting as delayed puberty in adolescence is relatively common, permanent hypogonadism presenting in infancy or adolescence is unusual. The main differential diagnoses of delayed puberty include self-limited delayed puberty (DP), idiopathic hypogonadotropic hypogonadism (IHH) and hypergonadotropic hypogonadism. Treatment of self-limited DP involves expectant observation or short courses of low dose sex steroid supplementation. More complex and involved management is required in permanent hypogonadism to achieve both development of secondary sexual characteristics and to maximize the potential for fertility. This review will cover the options for management involving sex steroid or gonadotropin therapy, with discussion of benefits, limitations and specific considerations of the different treatment options.

Amniotic Fluid INSL3 Measured During the Critical Time Window in Human Pregnancy Relates to Cryptorchidism, Hypospadias, and Phthalate Load: A Large Case-Control Study

The period of the first to second trimester transition in human pregnancy represents a sensitive window for fetal organogenesis, particularly in regard to the development of the male reproductive system. This is a time of relative analytical inaccessibility. We have used a large national biobank of amniotic fluid samples collected at routine amniocentesis to determine the impacts of exogenous endocrine disruptor load on specific fetal biomarkers at this critical time. While adrenal and testicular steroids are highly correlated, they are also mostly positively influenced by increasing phthalate load, represented by the metabolites 7cx-MMeHP and 5cx-MEPP, by perfluorooctane sulfonate (PFOS) exposure, and by smoking, suggesting an adrenal stress response. In contrast, the testis specific biomarkers insulin-like peptide 3 (INSL3) and androstenedione are negatively impacted by the phthalate endocrine disruptors. Using a case-control design, we show that cryptorchidism and hypospadias are both significantly associated with increased amniotic concentration of INSL3 during gestational weeks 13-16, and some, though not all steroid biomarkers. Cases are also linked to a specifically increased variance in the Leydig cell biomarker INSL3 compared to controls, an effect exacerbated by maternal smoking. No influence of phthalate metabolites or PFOS was evident on the distribution of cases and controls. Considering that several animal and human studies have shown a negative impact of phthalate load on fetal and cord blood INSL3, respectively, the present results suggest that such endocrine disruptors may rather be altering the relative dynamics of testicular development and consequent hormone production, leading to a desynchronization of tissue organization during fetal development. Being born small for gestational age appears not to impact on the testicular biomarker INSL3 in second trimester amniotic fluid.

Postnatal Changes in Testicular Position Are Associated With IGF-I and Function of Sertoli and Leydig Cells

CONTEXT

Despite clinical guidelines calling for repetitive examination of testicular position during childhood, little is known of normal changes in testicular position during childhood, let alone factors that control it.

OBJECTIVE

To assess changes in and factors associated with testicular position during childhood.

DESIGN

Testicular position (the distance from the pubic bone to the upper pole of the testes) at birth, 3 months, 18 months, 36 months, and 7 years and reproductive hormones at 3 months were measured.

SETTING

Prenatally recruited, prospective longitudinal birth cohort.

PARTICIPANTS

A total of 2545 boys were recruited prenatally in a Danish-Finnish birth cohort and had a testicular position examination available. A subset of 680 Danish and 362 Finnish boys had serum reproductive hormone concentrations and insulin-like growth factor I (IGF-I) determined at 3 months.

MAIN OUTCOME MEASURES

Testicular distance to pubic bone (TDP), serum reproductive hormone, and IGF-I concentrations.

RESULTS

TDP increased from birth to 3 months and decreased thereafter. Length, gestational age, weight for gestational age, and penile length were positively associated with larger TDP and thus lower testicular position in a linear mixed-effect model. Furthermore, IGF-I concentration, inhibin B/follicle-stimulating hormone ratio, and testosterone/luteinizing hormone ratio were all independently and positively associated with longer TDP.

CONCLUSIONS

We provide longitudinal data on postnatal changes in TDP. TDP is dynamic and associated with Leydig and Sertoli cell function as well as with IGF-I levels during the first months of life at mini-puberty of infancy. TDP may thus be a useful biomarker of postnatal testicular function.

Anti-Müllerian Hormone and Testicular Function in Prepubertal Boys With Cryptorchidism

INTRODUCTION

The functional capacity of the testes in prepubertal boys with cryptorchidism before treatment has received very little attention. The assessment of testicular function at diagnosis could be helpful in the understanding of the pathophysiology of cryptorchidism and in the evaluation of the effect of treatment. Anti-Müllerian hormone is a well-accepted Sertoli cell biomarker to evaluate testicular function during childhood without the need for stimulation tests.

OBJECTIVE

The aim of the study was to assess testicular function in prepubertal children with cryptorchidism before orchiopexy, by determining serum anti-Müllerian hormone (AMH). We also evaluated serum gonadotropins and testosterone and looked for associations between testicular function and the clinical characteristics of cryptorchidism.

MATERIALS AND METHODS

We performed a retrospective, cross-sectional, analytical study at a tertiary pediatric public hospital. All clinical charts of patients admitted at the outpatient clinic, and recorded in our database with the diagnosis of cryptorchidism, were eligible. The main outcome measure of the study was the serum concentration of AMH. Secondary outcome measures were serum LH, FSH, and testosterone. For comparison, serum hormone levels from a normal population of 179 apparently normal prepubertal boys were used.

RESULTS

Out of 1,557 patients eligible in our database, 186 with bilateral and 124 with unilateral cryptorchidism were selected using a randomization software. Median AMH standard deviation score was below 0 in both the bilaterally and the unilaterally cryptorchid groups, indicating that testicular function was overall decreased in patients with cryptorchidism. Serum AMH was significantly lower in boys with bilateral cryptorchidism as compared with controls and unilaterally cryptorchid patients between 6 months and 1.9 years and between 2 and 8.9 years of age. Serum AMH below the normal range reflected testicular dysfunction in 9.5-36.5% of patients according to the age group in bilaterally cryptorchid boys and 6.3-16.7% in unilaterally cryptorchid boys. FSH was elevated in 8.1% and LH in 9.1% of boys with bilateral cryptorchidism, most of whom were anorchid. In patients with present testes, gonadotropins were only mildly elevated in less than 5% of the cases. Basal testosterone was mildly decreased in patients younger than 6 months old, and uninformative during childhood.

CONCLUSION

Prepubertal boys with cryptorchidism, especially those with bilaterally undescended gonads, have decreased AMH production. Although serum AMH may fall within the normal range, there is a considerable prevalence of testicular dysfunction during childhood in this frequent condition.

Perspective: A Neuro-Hormonal Systems Approach to Understanding the Complexity of Cryptorchidism Susceptibility

Nonsyndromic cryptorchidism is a common multifactorial, condition with long-term risks of subfertility and testicular cancer. Revealing the causes of cryptorchidism will likely improve prediction and prevention of adverse outcomes. Herein we provide our current perspective of cryptorchidism complexity in a synthesis of cumulative clinical and translational data generated by ourselves and others. From our recent comparison of genome-wide association study (GWAS) data of cryptorchidism with or without testicular germ cell tumor, we identified RBFOX family genes as candidate susceptibility loci. Notably, RBFOX proteins regulate production of calcitonin gene-related peptide (CGRP), a sensory neuropeptide linked to testicular descent in animal models. We also re-analyzed existing fetal testis transcriptome data from a rat model of inherited cryptorchidism (the LE/orl strain) for enrichment of Leydig cell progenitor genes. The majority are coordinately downregulated, consistent with known reduced testicular testosterone levels in the LE/orl fetus, and similarly suppressed in the gubernaculum. Using qRT-PCR, we found dysregulation of dorsal root ganglia (DRG) sensory transcripts ipsilateral to undescended testes. These data suggest that LE/orl cryptorchidism is associated with altered signaling in possibly related cell types in the testis and gubernaculum as well as DRG. Complementary rat and human studies thus lead us to propose a multi-level, integrated neuro-hormonal model of testicular descent. Variants in genes encoding RBFOX family proteins and/or their transcriptional targets combined with environmental exposures may disrupt this complex pathway to enhance cryptorchidism susceptibility. We believe that a systems approach is necessary to provide further insight into the causes and consequences of cryptorchidism.

Endocrine Disrupting Chemicals Interfere With Leydig Cell Hormone Pathways During Testicular Descent in Idiopathic Cryptorchidism

Cryptorchidism, a frequent genital malformation in male newborn, remains in most cases idiopathic. On the basis of experimental, epidemiological, and clinical data, it has been included in the testicular dysgenesis syndrome and believed to be influenced, together with genetic and anatomic factors, by maternal exposure to endocrine disrupting chemicals (EDCs). Here, we analyze how EDCs may interfere with the control of testicular descent, which is regulated by two Leydig cell hormones, testosterone, and insulin like peptide 3 (INSL3).

Circulating anti-Müllerian hormone (AMH) associates with the maturity of boys' drawings: Does AMH slow cognitive development in males?

PURPOSE

High levels of circulating anti-Müllerian hormone are unique to developing males, but the function of anti-Müllerian hormone in boys is unknown. In mice, anti-Müllerian hormone contributes to the male biases in the brain, but its receptors are present throughout non-sexually dimorphic portions of the brain. In humans, the speed of maturation is the most overt difference between girls and boys. We postulate that this is because anti-Müllerian hormone slows the maturation of the male human brain.

METHODS

One hundred and fourty three 5-year or 6-year-old boys and 38 age-matched girls drew a person and donated a blood sample. The children's drawings were blind-scored to generate a maturity index. The level of anti-Müllerian hormone and the other Sertoli cell hormone, inhibin B, were measured by ELISA. The relationship between the children's age, hormones and maturity index were examined by linear regression analysis.

RESULTS

The girls drew more complex and realistic person than the boys (32%, p = 0.001), with their drawings also being larger (39%, p = 0.037) and more coloured-in (235%, p = 0.0005). The maturity index in boys correlated with age (+r = 0.43, p < 0.0005) and anti-Müllerian hormone level (-r = -0.29, p < 0.0005). The association between maturity index and anti-Müllerian hormone level persisted when corrected for age and for inhibin B (r = -0.24, p = 0.0005). The calculated effect of the median level of anti-Müllerian hormone (1 nM) was equal to 0.81 months of development. The size and colouring of the drawings did not correlate with the boys' age, anti-Müllerian hormone or inhibin B.

CONCLUSIONS

This exploratory study provides the first indicative evidence that circulating anti-Müllerian hormone may influence the development of the human brain.

Postnatal testosterone may be an important mediator of the association between prematurity and male neurodevelopmental disorders: a hypothesis

Children born premature are at risk for neurodevelopmental disorders, including autism and schizophrenia. This piece advances the hypothesis that altered androgen exposure observed in premature infants is an important mediator of the neurodevelopmental risk in males associated with prematurity. Specifically, the alterations of normative physiologic postnatal activations of the hypothalamic-pituitary-gonadal axis that occur in preterm males are hypothesized to contribute to the risk of neuropsychiatric pathology of prematurity through altered androgen-mediated organizational effects on the developing brain. The physiology of testosterone and male central nervous system development in full-term births is reviewed and compared to the developmental processes of prematurity. The effects of the altered testosterone physiology observed within prematurity outside of the central nervous system are reviewed as a segue into a discussion of the effects within the nervous system, with a special focus on autism spectrum disorders and attention deficit hyperactivity disorder. The explanatory power of this model is reviewed as a supplement to the preexisting models of prematurity and neurodevelopmental risk, including infection and other perinatal central nervous system insults. The emphasis is placed on altered androgen exposure as serving as just one among many mediators of neurodevelopmental risk that may be of interest for further research and evidence-based investigation. Implications for diagnosis, management and preventative treatments conclude the piece.

Relaxin-like peptides in male reproduction - a human perspective

The relaxin family of peptide hormones and their cognate GPCRs are becoming physiologically well-characterized in the cardiovascular system and particularly in female reproductive processes. Much less is known about the physiology and pharmacology of these peptides in male reproduction, particularly as regards humans. H2-relaxin is involved in prostate function and growth, while insulin-like peptide 3 (INSL3) is a major product of the testicular Leydig cells and, in the adult, appears to modulate steroidogenesis and germ cell survival. In the fetus, INSL3 is a key hormone expressed shortly after sex determination and is responsible for the first transabdominal phase of testicular descent. Importantly, INSL3 is becoming a very useful constitutive biomarker reflecting both fetal and post-natal development. Nothing is known about roles for INSL4 in male reproduction and only very little about relaxin-3, which is mostly considered as a brain peptide, or INSL5. The former is expressed at very low levels in the testes, but has no known physiology there, whereas the INSL5 knockout mouse does exhibit a testicular phenotype with mild effects on spermatogenesis, probably due to a disruption of glucose homeostasis. INSL6 is a major product of male germ cells, although it is relatively unexplored with regard to its physiology or pharmacology, except that in mice disruption of the INSL6 gene leads to a disruption of spermatogenesis. Clinically, relaxin analogues may be useful in the control of prostate cancer, and both relaxin and INSL3 have been considered as sperm adjuvants for in vitro fertilization.

LINKED ARTICLES

This article is part of a themed section on Recent Progress in the Understanding of Relaxin Family Peptides and their Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.10/issuetoc.