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

Longitudinal Sex Steroid Data in Relation to Birth Weight in Preterm Boys

CONTEXT

There is a lack of knowledge on longitudinal sex steroid patterns during infancy, especially for boys born preterm or with low birth weight (LBW).

OBJECTIVE

To find out whether LBW boys have a disturbed sex steroid profile during infancy.

DESIGN AND SETTING

Population-based longitudinal study performed at Sahlgrenska University Hospital, Gothenburg, Sweden.

PARTICIPANTS

Ninety-eight singleton boys (47 LBW) born at gestational age 32.0 to 36.9 weeks were included. Because of dropout, 83 of the boys were still in the study at 10 months' corrected age.

MAIN OUTCOME MEASURES

Serum androgen and estrogen concentrations were analyzed by gas chromatography-tandem mass spectrometry and IGF-I was determined with radioimmunoassay in umbilical cord and at 0, 2, 5, and 10 months' corrected age.

RESULTS

Serum levels of androstenedione, estrone, and estradiol declined gradually from birth to 10 months corrected age. In both LBW boys and their counterparts, a surge was seen at 2 months' corrected age (3 months' chronological age) for testosterone, median (range) 6.5 (2.0-18.9) nmol/L, and in dihydrotestosterone 1.2 (0.4-4.3) nmol/L. At birth, LBW boys had higher median testosterone (0.7 vs 0.4 nmol/L, P = 0.019), and at 0 months' corrected age, both had higher testosterone (5.7 vs 3.5 nmol/L, P = 0.003) and dihydrotestosterone (1.2 vs 0.9 nmol/L, P = 0.006) than their counterparts. At 10 months' corrected age, catch-up in weight SD score from birth correlated with testosterone (rho = 0.27, P = 0.044) and androstenedione (rho = 0.29, P = 0.027).

CONCLUSIONS

Moderately to late preterm LBW boys showed a disturbed sex hormone profile, with elevated concentrations of androgens in early infancy.

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.

Current concepts surrounding neonatal hormone therapy for boys with congenital hypogonadotropic hypogonadism

INTRODUCTION

Congenital hypogonadotropic hypogonadism (CHH) is a genetic disorder of reproduction and development, characterized by deficient gonadotropin-releasing hormone (GnRH) secretion or action, affecting 1-in-4,000-15,000 males. Micropenis and undescended testes are cardinal features of antenatal GnRH deficiency and could indicate absent minipuberty in the first postnatal months. In this review, we outline the pathophysiology and clinical consequences of absent minipuberty and its implications for optimal approaches to the endocrine management of affected boys.

AREAS COVERED

Deficient GnRH activity during fetal development and neonatal-infancy phase of minipuberty accounts for the diminished mass of Sertoli cells and seminiferous tubules among CHH males, enduring impairment of reproductive function even during gonadotropin replacement in adult life. In overcoming this obstacle, several clinical studies of neonatal gonadotropin replacement have consistently shown positive results in inducing testicular development and correcting cryptorchidism.

EXPERT OPINION

A high index of clinical suspicion, combined with hormonal testing undertaken in the postnatal period of 1-4 months, can reliably confirm or refute the diagnosis of CHH. Timely identification of CHH in affected male infants (having characteristic "red flag' developmental anomalies) opens up the possibility for gonadotropin replacement as a targeted therapy to restore the normal hormonal milieu of minipuberty. Further work is necessary in formulating optimal gonadotropin treatment regimens to be more widely adopted in clinical practice.

Open controversies on the treatment of undescended testis: An update

Cryptorchidism is a common congenital malformation in pediatric urology. Although there have been many studies on the etiology of the disease, it has not been fully clarified, and while its diagnostic and treatment models have gradually approached standardization and systematization, some controversies regarding treatment remain. Additionally, although ultrasound is a non-invasive examination without ionizing radiation, its role in the evaluation of cryptorchidism remains controversial. The main basis for treating cryptorchidism is orchidopexy, and the main view on treatment age is that treatment should be performed between 6 and 12 months after birth, but no more than 18 months after birth. The view on hormone therapy is still controversial because most scholars believe that early surgery is the key to treatment. There are many surgical treatment methods for cryptorchidism, including traditional open surgery and laparoscopic surgery, which provide satisfactory results. In conclusion, the treatment of undescended testis (UDT) had been largely standardized, apart from the treatment of high intra-abdominal testis (IAT), which remains a matter of debate.

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.

During infancy low levels of follicle-stimulating hormone may result in high rate of germ cell apoptosis

PURPOSE

It has been suggested that follicle-stimulating hormone (FSH) plays a role in preventing germ cell apoptosis. We aimed to compare apoptotic rate of boys with cryptorchidism having different levels of FSH in order to investigate its role in apoptosis.

METHODS

Hormonal profiles and testicular biopsies from 30 boys with unilateral cryptorchidism (age range: 4-14 months) were included. Based on FSH level, the boys were grouped into three (3 × 10) having high (>97.5percentile), low (<2.5percentile), or within normal range. Sections underwent immunohistochemical staining to analyze the number of germ cells and type A dark spermatogonia per cross-sectional tubule. One section was co-stained with immunofluorescent antibodies against an apoptotic marker (cleaved caspase-3), proliferation marker (Ki67), Sertoli cell marker (anti-Müllerian hormone) and processed by confocal imaging for analysis. Germ cell apoptosis was calculated as the apoptosis index (percentage caspase-3+ germ cells/total germ cell number).

RESULTS

Fifty percent (5/10) of the boys with low FSH had an apoptosis index above 90% compared with 15% (3/20) of the boys with normal or high FSH (p = 0.04). Caspase-3+ germ cells were most likely to be located on the basement membrane (p<0.05).

CONCLUSION

Our findings lead to trends proposing that FSH may play a role in preventing apoptosis.

TYPE OF STUDY

Prognosis Study LEVEL OF EVIDENCE: III.

Maternal serum concentrations of bisphenol A and propyl paraben in early pregnancy are associated with male infant genital development

STUDY QUESTION

Are maternal serum phthalate metabolite, phenol and paraben concentrations measured at 10-17 weeks of gestation associated with male infant genital developmental outcomes, specifically cryptorchidism, anogenital distance (AGD), penile length and testicular descent distance, at birth and postnatally?

SUMMARY ANSWER

Maternal serum bisphenol A (BPA) concentration at 10-17 weeks of gestation was positively associated with congenital or postnatally acquired cryptorchidism, and n-propyl paraben (n-PrP) concentration was associated with shorter AGD from birth to 24 months of age.

WHAT IS KNOWN ALREADY

Male reproductive disorders are increasing in prevalence, which may reflect environmental influences on foetal testicular development. Animal studies have implicated phthalates, BPA and parabens, to which humans are ubiquitously exposed. However, epidemiological studies have generated conflicting results and have often been limited by small sample size and/or measurement of chemical exposures outside the most relevant developmental window.

STUDY DESIGN, SIZE, DURATION

Case-control study of cryptorchidism nested within a prospective cohort study (Cambridge Baby Growth Study), with recruitment of pregnant women at 10-17 postmenstrual weeks of gestation from a single UK maternity unit between 2001 and 2009 and 24 months of infant follow-up. Of 2229 recruited women, 1640 continued with the infancy study after delivery, of whom 330 mothers of 334 male infants (30 with congenital cryptorchidism, 25 with postnatally acquired cryptorchidism and 279 unmatched controls) were included in the present analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Maternal blood was collected at enrolment, and serum levels of 16 phthalate metabolites, 9 phenols (including BPA) and 6 parabens were measured using liquid chromatography/tandem mass spectrometry. Logistic regression was used to model the association of cryptorchidism with serum chemical concentrations, adjusting for putative confounders. Additionally, offspring AGD, penile length and testicular descent distance were assessed at 0, 3, 12, 18 and 24 months of age, and age-specific Z scores were calculated. Associations between serum chemical levels and these outcomes were tested using linear mixed models.

MAIN RESULTS AND THE ROLE OF CHANCE

Maternal serum BPA concentration was associated with offspring all-type cryptorchidism both when considered as a continuous exposure (adjusted odds ratio per log10 μg/l: 2.90, 95% CI 1.31-6.43, P =  0.009) and as quartiles (phet =  0.002). Detection of n-PrP in maternal serum was associated with shorter AGD (by 0.242 standard deviations, 95% CI 0.051-0.433, P =  0.01) from birth to 24 months of age; this reduction was independent of body size and other putative confounders. We did not find any consistent associations with offspring outcomes for the other phenols, parabens, and phthalate metabolites measured.

LIMITATIONS, REASONS FOR CAUTION

We cannot discount confounding by other demographic factors or endocrine-disrupting chemicals. There may have been misclassification of chemical exposure due to use of single serum measurements. The cohort was not fully representative of pregnant women in the UK, particularly in terms of smoking prevalence and maternal ethnicity.

WIDER IMPLICATIONS OF THE FINDINGS

Our observational findings support experimental evidence that intrauterine exposure to BPA and n-PrP during early gestation may adversely affect male reproductive development. More evidence is required before specific public health recommendations can be made.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by a European Union Framework V programme, the World Cancer Research Fund International, the Medical Research Council (UK), Newlife the Charity for Disabled Children, the Mothercare Group Foundation, Mead Johnson Nutrition and the National Institute for Health Research Cambridge Comprehensive Biomedical Research Centre. Visiting Fellowship (J.M.): Regional Programme 'Jiménez de la Espada' for Research Mobility, Cooperation and Internationalization, Seneca Foundation-Science and Technology Agency for the Region of Murcia (No. 20136/EE/17). K.O. is supported by the Medical Research Council (UK) (Unit Programme number: MC_UU_12015/2). The authors declare no conflict of interest.

Recent advances in understanding and managing Kallmann syndrome

Many of the recent advances in our understanding of human reproductive biology and its genetic basis have arisen directly via the genetic investigation of patients with Kallmann syndrome and their families. The disease is characterised by the association of an isolated defect in the secretion (or, less commonly, action) of gonadotropin-releasing hormone (GnRH) and consequent infertility, with anosmia and potentially other associated non-reproductive features. GnRH-producing neurons are located in the hypothalamic brain region after a peculiar migration during embryonic life. To date, different genes affecting GnRH neuron development/migration have so far been implicated in Kallmann syndrome, but our knowledge of the genetic basis of the syndrome remains incomplete. From a clinical point of view, the disease has suffered from a lack of definitive diagnosis and treatment, and although progress has been made in terms of timely diagnosis and evidence-based treatment of patients, implementation remains inconsistent. These aspects will be discussed in this review, which examines new strategies for arriving at more evidence-based and patient-centred medical practice in Kallmann syndrome.

Somatotropic-Testicular Axis: A crosstalk between GH/IGF-I and gonadal hormones during development, transition, and adult age

BACKGROUND

The hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-somatotropic (HPS) axes are strongly interconnected. Interactions between these axes are complex and poorly understood. These interactions are characterized by redundancies in reciprocal influences at each level of regulation and the combination of endocrine and paracrine effects that change during development.

OBJECTIVES

To comprehensively review the crosstalk between the HPG and HPS axes and related pathological and clinical aspects during various life stages of male subjects.

MATERIALS AND METHODS

A thorough search of publications available in PubMed was performed using proper keywords.

RESULTS

Molecular studies confirmed the expressions of growth hormone (GH) and insulin-like growth factor-I (IGF-I) receptors on the HPG axis and reproductive organs, indicating a possible interaction between HPS and HPG axes at various levels. Insulin growth factors participate in sexual differentiation during fetal development, indicating that normal HPS axis activity is required for proper testicular development. IGF-I contributes to correct testicular position during minipuberty, determines linear growth during childhood, and promotes puberty onset and pace through gonadotropin-releasing hormone activation. IGF-I levels are high during transition age, even when linear growth is almost complete, suggesting its role in reproductive tract maturation. Patients with GH deficiency (GHD) and insensitivity (GHI) exhibit delayed puberty and impaired genital development; replacement therapy in such patients induces proper pubertal development. In adults, few studies have suggested that lower IGF-I levels are associated with impaired sperm parameters.

DISCUSSION AND CONCLUSION

The role of GH-IGF-I in testicular development remains largely unexplored. However, it is important to evaluate gonadic development in children with GHD. Additionally, HPS axis function should be evaluated in children with urogenital malformation or gonadal development alterations. Correct diagnosis and prompt therapeutic intervention are needed for healthy puberty, attainment of complete gonadal development during transition age, and fertility potential in adulthood.

Expression of the Insulin-like Growth Factor System in First- and Second-Trimester Human Embryonic and Fetal Gonads

CONTEXT

Insulin-like growth factor (IGF) signaling is crucial for sex differentiation and development of Leydig and Sertoli cells in fetal mice testes. No such information is available for human embryonic and fetal testes and ovaries.

OBJECTIVE

To investigate presence and activity of the IGF signaling system during human embryonic and fetal ovarian and testicular development.

DESIGN

Human embryonic and fetal gonads were obtained following legal terminations of pregnancies. Gene expression was assessed by microarray and qPCR transcript analyses. Proteins of the IGF system components were detected with immunohistochemistry and immunofluorescence analyses. Specimens were included from 2010 to 2017.

SETTING

University Hospital.

PATIENTS/PARTICIPANTS

Ovaries and testes from a total of 124 human embryos and fetuses aged 5 to 17 postconception weeks were obtained from healthy women aged 16 to 47 years resident in Denmark or Scotland.

MAIN OUTCOME MEASURES

Gene expression analysis using microarray was performed in 46 specimens and qPCR analysis in 56 specimens, both sexes included. Protein analysis included 22 specimens (11 ovaries, 11 testes).

RESULTS

IGF system members were detected in embryonic and fetal testes and ovaries, both at gene transcript and protein level. A higher expression of IGF regulators was detected in testes than ovaries, with a preferred localization to Leydig cells.

CONCLUSIONS

These data indicate that the IGF system is active during very early gestation, when it may have a regulatory role in Leydig cells.

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.

Why Do Normal Children Have Acromegalic Levels of IGF-I During Puberty?

CONTEXT

The rapid pubertal height growth is unique to humans, but why do we have it? Although the spurt contributes 13% to 15% to the final adult height, we hypothesized that the biological significance of the high acromegalic levels of GH and IGF-I, which are behind the pubertal growth spurt, might primarily occur to stimulate the reproductive organs.

EVIDENCE SYNTHESIS

Animal data have demonstrated that adult Igf1 and Igf2 gene knockout mice that survive show a dramatic reduction in the size of the reproductive organs and are infertile. In humans, case reports of mutations in the genes affecting the GH-IGF axis and growth (GH, GHRH, GH-R, STAT5b, IGF-I, IGF-II, IGF-1R, PAPPA2) are also characterized by delayed pubertal onset and micropenis. Furthermore, GH treatment will tend to normalize the penile size in patients with GH deficiency. Thus, the endocrine effects of high IGF-I levels might be needed for the transition of the sexual organs, including the secondary sex characteristics, from the "dormant" stages of childhood into fully functioning reproductive systems. The peak IGF-I levels, on average, occur 2 years after the peak height growth velocity, suggesting reasons other than longitudinal growth for the high IGF-I levels, and remain high in the years after the height spurt, when the reproductive systems become fully functional.

CONCLUSION

We suggest that the serum levels of IGF-I should be monitored in children with poor development of sexual organs, although it remains to be investigated whether GH should be added to sex steroids in the management of hypogonadism for some pubertal children (e.g., boys with micropenis).

The IGF1 Receptor Is Involved in Follicle-Stimulating Hormone Signaling in Porcine Neonatal Sertoli Cells

Experimental evidence has shown that the IGF1 receptor (IGF1R) is involved in testicular development during embryogenesis. More recently, data gathered from mice granulosa cells and zebrafish spermatogonia suggest that IGF1R has a role in Follicle-stimulating hormone (FSH) signaling. No evidence has been reported on this matter in Sertoli cells (SCs) so far. The aim of the study was to evaluate the role, if any, of the IGF1R in FSH signaling in SCs. The effects of FSH exposure on myosin-phosphatase 1 (MYPT1), ERK 1/2, AKT³⁰⁸, AKT⁴⁷³, c-Jun N-terminal kinase (JNK) phosphorylation and on anti-Müllerian hormone (AMH), inhibin B and FSH receptor (FSHR) mRNA levels were assessed with and without the IGF1R inhibitor NVP-AEW541 in purified and functional porcine neonatal SCs. Pre-treatment with NVP-AEW541 inhibited the FSH-induced MYPT1 and ERK 1/2 phosphorylation, decreased the FSH-dependent Protein kinase B (AKT)³⁰⁸ phosphorylation, but did not affect the FSH-induced AKT⁴⁷³ and JNK phosphorylation rate. It also interfered with the FSH-induced AMH and FSHR down-regulation. No influence was observed on the FSH-stimulated Inhibin B gene expression. Conclusion. These findings support the role of theIGF1R in FSH signaling in porcine SCs. The possible influence of IGF1 stimulation on the FSH-mediated effects on SCs should be further explored.

Congenital Hypogonadotrophic Hypogonadism: Minipuberty and the Case for Neonatal Diagnosis

Congenital hypogonadotrophic hypogonadism (CHH) is a rare but important etiology of pubertal failure and infertility, resulting from impaired gonadotrophin-releasing hormone secretion or action. Despite the availability of effective hormonal therapies, the majority of men with CHH experience unsatisfactory outcomes, including chronic psychosocial and reproductive sequelae. Early detection and timely interventions are crucial to address the gaps in medical care and improve the outlook for these patients. In this paper, we review the clinical implications of missing minipuberty in CHH and therapeutic strategies that can modify the course of disease, as well as explore a targeted approach to identifying affected male infants by integrating clinical and biochemical data in the early postnatal months.

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.

Managing congenital hypogonadotrophic hypogonadism: a contemporary approach directed at optimizing fertility and long-term outcomes in males

Hormonal induction of spermatogenesis offers men with azoospermia due to hypogonadotrophic hypogonadism (HH) the promising prospect of fertility restoration. However, an important exception is the subset of individuals affected by congenital hypogonadotrophic hypogonadism (CHH), also known as Kallmann syndrome if associated with anosmia, who often display dismal responses to fertility induction, despite prolonged therapy. This primarily stems from the loss of minipuberty, which is a crucial phase of testicular maturation in early life that has a far-reaching impact on eventual spermatogenic capacity. Further exacerbating the compromised reproductive health is the failure to initiate timely pubertal induction in many CHH patients, resulting in suboptimal genital and psychosexual development. In this paper, the clinical implications and management of male HH across the lifespan is comprehensively reviewed, with a special focus on novel strategies that have the potential to modify disease severity and maximize fertility potential in CHH by addressing the inadequacies of conventional approaches.

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.

Evaluation of testicular function in prepubertal children

INTRODUCTION

The assessment of testicular function is not currently performed in childhood. The aim of this review was to address the usefulness of serum Anti-Müllerian Hormone (AMH), inhibin B, and testicular volume (TV) evaluation in children.

REVIEW

Serum AMH and inhibin B levels reflect Sertoli cells (SCs) health and number, SCs maturation degree and their exposure to FSH and to intra-tubular testosterone (T). These hormones might be helpful in discriminating between congenital central hypogonadism (cHH) and constitutional delay in growth and puberty (CDGP) and in case of clinical suspicious of precocious puberty. Furthermore, low AMH and/or inhibin B levels have been observed in children with primary testicular disorders, suggesting the existence of SC dysfunction. TV also provides useful information on testicular health. Recently, a medical calculator, requiring testis length and the stage of genital development, has been developed to easily derive TV.

CONCLUSIONS

The evidence supports the usefulness of AMH, inhibin B and TV evaluation for the early diagnosis of puberty disorders and primary testicular damage. We suggest the measurement of TV by using the medical calculator in all children and to reserve AMH and inhibin B measurements to those cases of no testicular growth, clinical suspicious of puberty disorders or in children at risk for spermatogenesis damage. This work-up might allow the early detection of testicular tubular damage which, in turn, may be useful to prevent the oncoming male infertility in adulthood.

Up-To-Date Review About Minipuberty and Overview on Hypothalamic-Pituitary-Gonadal Axis Activation in Fetal and Neonatal Life

Minipuberty consists of activation of the hypothalamic-pituitary-gonadal (HPG) axis during the neonatal period, resulting in high gonadotropin and sex steroid levels, and occurs mainly in the first 3-6 months of life in both sexes. The rise in the levels of these hormones allows for the maturation of the sexual organs. In boys, the peak testosterone level is associated with penile and testicular growth and the proliferation of gonadic cells. In girls, the oestradiol levels stimulate breast tissue, but exhibit considerable fluctuations that probably reflect the cycles of maturation and atrophy of the ovarian follicles. Minipuberty allows for the development of the genital organs and creates the basis for future fertility, but further studies are necessary to understand its exact role, especially in girls. Nevertheless, no scientific study has yet elucidated how the HPG axis turns itself off and remains dormant until puberty. Additional future studies may identify clinical implications of minipuberty in selected cohorts of patients, such as premature and small for gestational age infants. Finally, minipuberty provides a fundamental 6-month window of the possibility of making early diagnoses in patients with suspected sexual reproductive disorders to enable the prompt initiation of treatment rather than delaying treatment until pubertal failure.