Serum insulin-like factor 3 is highly correlated with intratesticular testosterone in normal men with acute, experimental gonadotropin deficiency stimulated with low-dose human chorionic gonadotropin: a randomized, controlled trial

Serum Insulin-like Factor 3, Testosterone, and LH in Experimental and Therapeutic Testicular Suppression

BACKGROUND

Serum insulin-like factor 3 (INSL3) is a Leydig cell biomarker, but little is known about the circulating concentration of INSL3 during hypothalamus-pituitary-testicular suppression.

AIM

To study the concomitant changes in serum concentrations of INSL3, testosterone, and LH during experimental and therapeutic testicular suppression.

METHODS

We included serum samples from 3 different cohorts comprising subjects before and after testicular suppression: (1) 6 healthy young men who were treated with androgens (Sustanon, Aspen Pharma, Dublin, Ireland); 2) 10 transgender girls (male sex assigned at birth) who were treated with 3-monthly GnRH agonist injections (Leuprorelinacetat, Abacus Medicine, Copenhagen, Denmark); and (3) 55 patients with prostate cancer who were randomized to surgical castration (bilateral subcapsular orchiectomy) or treatment with GnRH agonist (Triptorelin, Ipsen Pharma, Kista, Sweden). Serum INSL3 and testosterone concentrations were quantified in stored serum samples using validated liquid chromatography-tandem mass spectrometry methodologies, and LH was measured by an ultrasensitive immunoassay.

RESULTS

The circulating concentrations of INSL3, testosterone, and LH decreased during experimental testicular suppression in healthy young men by Sustanon injections and subsequently returned to baseline levels after release of suppression. All 3 hormones decreased during therapeutic hormonal hypothalamus-pituitary-testicular suppression in transgender girls and in patients with prostate cancer.

CONCLUSION

INSL3 resembles testosterone as a sensitive marker of testicular suppression and reflects Leydig cell function, also during exposure to exogenous testosterone. Serum INSL3 measurements may complement testosterone as a Leydig cell marker in male reproductive disorders, during therapeutic testicular suppression as well as in surveillance of illicit use of androgens.

Effect of Mitotane on Male Gonadal Function

BACKGROUND

Clinical evidence has shown frequent hypogonadism following mitotane (MTT) treatment in male patients with adrenocortical carcinoma. This study aimed to evaluate the impact of MTT on male gonadal function.

METHODS

Morphological analysis of testes and testosterone assays were performed on adult CD1 MTT-treated and untreated mice. The expression of key genes involved in interstitial and tubular compartments was studied by real-time PCR. Moreover, quantitative and qualitative analysis of spermatozoa was performed.

RESULTS

Several degrees of damage to the testes and a significant testosterone reduction in MTT-treated mice were observed. A significant decline in 3βHsd1 and Insl3 mRNA expression in the interstitial compartment confirmed an impairment of androgen production. Fsh-R mRNA expression was unaffected by MTT, proving that Sertoli cells are not the drug's primary target. Sperm concentrations were significantly lower in MTT-treated animals. Moreover, the drug caused a significant increase in the percentage of spermatozoa with abnormal chromatin structures.

CONCLUSION

MTT negatively affects the male reproductive system, including changes in the morphology of testicular tissue and reductions in sperm concentration and quality.

Testosterone Serum Levels Are Related to Sperm DNA Fragmentation Index Reduction after FSH Administration in Males with Idiopathic Infertility

Purpose: Although a robust physiological rationale supports follicle stimulating hormone (FSH) use in male idiopathic infertility, useful biomarkers to evaluate its efficacy are not available. Thus, the primary aim of the study was to evaluate if testosterone serum levels are related to sperm DNA fragmentation (sDF) index change after FSH administration. The secondary aim was to confirm sDF index validity as a biomarker of FSH administration effectiveness in male idiopathic infertility. Methods: A retrospective, post-hoc re-analysis was performed on prospectively collected raw data of clinical trials in which idiopathic infertile men were treated with FSH and both testosterone serum levels and sDF were reported. Results: Three trials were included, accounting for 251 patients. The comprehensive analysis confirmed FSH’s beneficial effect on spermatogenesis detected in each trial. Indeed, an overall significant sDF decrease (p < 0.001) of 20.2% of baseline value was detected. Although sDF resulted to be unrelated to testosterone serum levels at baseline, a significant correlation was highlighted after three months of FSH treatment (p = 0.002). Moreover, testosterone serum levels and patients’ age significantly correlated with sDF (p = 0.006). Dividing the cohort into responders/not responders to FSH treatment according to sDF change, the FSH effectiveness in terms of sDF improvement was related to testosterone and male age (p = 0.003). Conclusion: Exogenous FSH administration in male idiopathic infertility is efficient in reducing sDF basal levels by about 20%. In terms of sDF reduction, 59.2% of the patients treated were FSH-responders. After three months of FSH administration, a significant inverse correlation between sDF and testosterone was detected, suggesting an association between the FSH-administration-related sDF improvement and testosterone serum levels increase. These observations lead to the hypothesis that FSH may promote communications or interactions between Sertoli cells and Leydig cells.

Association of age, hormonal, and lifestyle factors with the Leydig cell biomarker INSL3 in aging men from the EMAS (European Male Aging Study) cohort

BACKGROUND

Aging in men is accompanied by a broad range of symptoms, including sexual dysfunction, cognitive and musculo-skeletal decline, obesity, type 2 diabetes, cardiovascular disease and hypertension, organ degeneration/failure, and increasing neoplasia, some of which are associated with declining levels of Leydig cell-produced testosterone. High natural biological variance, together with multiple factors that can modulate circulating testosterone concentration, may influence its interpretation and clinical implications. INSL3 is a biomarker of Leydig cell function that might provide complementary information on testicular health and its downstream outcomes.

OBJECTIVES

To characterize INSL3 as a biomarker to assess gonadal status in aging men.

METHODS & MATERIALS

The large European multi-centre EMAS cohort of community-dwelling men was analysed to determine how INSL3 relates to a range of hormonal, anthropometric, and lifestyle parameters.

RESULTS & DISCUSSION

INSL3 declines cross-sectionally and longitudinally within individuals at approximately 15% per decade from age 40, unlike testosterone (1.9% per decade), which is partly compensated by increasing pituitary LH production. Importantly, lower INSL3 in younger men appears to persist with aging. Multiple regression analysis shows that, unlike testosterone, INSL3 is negatively dependent on LH and SHBG, and positively on FSH, suggesting a different mechanism of gonadotropic regulation. Circulating INSL3 is negatively associated with increased BMI or waist circumference, and with smoking, and unlike testosterone is not affected by weight loss in the obese. Geographic variation in mean INSL3 within Europe appears to be largely explained by differences in these parameters. The results allow the establishment of a European-wide reference range for INSL3 (95% confidence interval) adjusted for increasing age.

CONCLUSION

INSL3 is a constitutive biomarker of Leydig cell functional capacity, being a robust, reliably measurable peptide, not subject to the gonadotropin-dependent short-term regulation and within-individual variation of testosterone. This article is protected by copyright. All rights reserved.

Impact of add-back FSH on human and mouse prostate following gonadotropin ablation by GnRH antagonist treatment

OBJECTIVE

During androgen ablation in prostate cancer by the standard gonadotropin-releasing hormone (GnRH) agonist treatment, only luteinizing hormone (LH) is permanently suppressed while circulating follicle-stimulating hormone (FSH) rebounds. We explored direct prostatic effects of add-back FSH, after androgen ablation with GnRH antagonist, permanently suppressing both gonadotropins.

METHODS

The effects of recombinant human (rFSH) were examined in mice treated with vehicle (controls), GnRH antagonist degarelix (dgx), dgx + rFSH, dgx + flutamide, or dgx + rFSH + flutamide for 4 weeks. Prostates and testes size and expression of prostate-specific and/or androgen-responsive genes were measured. Additionally, 33 young men underwent dgx-treatment. Seventeen were supplemented with rFSH (weeks 1-5), and all with testosterone (weeks 4-5). Testosterone, gondotropins, prostate-specific antigen (PSA), and inhibin B were measured.

RESULTS

In dgx and dgx + flutamide treated mice, prostate weight/body weight was 91% lower than in controls, but 41 and 11%, respectively, was regained by rFSH treatment (P = 0.02). The levels of seminal vesicle secretion 6, Pbsn, Nkx3.1, beta-microseminoprotein, and inhibin b were elevated in dgx + rFSH-treated animals compared with only dgx treated (all P < 0.05). In men, serum inhibin B rose after dgx treatment but was subsequently suppressed by testosterone. rFSH add-back had no effect on PSA levels.

CONCLUSIONS

These data provide novel evidence for the direct effects of FSH on prostate size and gene expression in chemically castrated mice. However, in chemically castrated men, FSH had no effect on PSA production. Whether FSH effects on the prostate in humans also require suppression of the residual adrenal-derived androgens and/or a longer period of rFSH stimulation, remains to be explored.

An update on male infertility and intratesticular testosterone-insight into novel serum biomarkers

Intratesticular testosterone is vital for spermatogenesis, male fertility, and virility. Currently the only method to assess levels of intratesticular testosterone is to perform testicular biopsy which is invasive and can lead to several complications. Approaches to assess intratesticular testosterone have been understudied but hold promise as future male contraceptive agents and may grant the ability to monitor patients undergoing hormonal changes from therapeutic and diagnostic perspectives. Previous studies have sought to assess the utility of 17-hydroxyprogesterone (17-OHP) and insulin-like factor 3 (INSL3) as accurate surrogate biomarkers of intratesticular testosterone. The aim of this review is thus to highlight the importance of intratesticular testosterone and the consequent advances that have been made to elucidate the potential of biomarkers for intratesticular testosterone in the context of male infertility.

The Roles of Luteinizing Hormone, Follicle-Stimulating Hormone and Testosterone in Spermatogenesis and Folliculogenesis Revisited

Spermatogenesis and folliculogenesis involve cell–cell interactions and gene expression orchestrated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). FSH regulates the proliferation and maturation of germ cells independently and in combination with LH. In humans, the requirement for high intratesticular testosterone (T) concentration in spermatogenesis remains both a dogma and an enigma, as it greatly exceeds the requirement for androgen receptor (AR) activation. Several data have challenged this dogma. Here we report our findings on a man with mutant LH beta subunit (LHβ) that markedly reduced T production to 1–2% of normal., but despite this minimal LH stimulation, T production by scarce mature Leydig cells was sufficient to initiate and maintain complete spermatogenesis. Also, in the LH receptor (LHR) knockout (LuRKO) mice, low-dose T supplementation was able to maintain spermatogenesis. In addition, in antiandrogen-treated LuRKO mice, devoid of T action, the transgenic expression of a constitutively activating follicle stimulating hormone receptor (FSHR) mutant was able to rescue spermatogenesis and fertility. Based on rodent models, it is believed that gonadotropin-dependent follicular growth begins at the antral stage, but models of FSHR inactivation in women contradict this claim. The complete loss of FSHR function results in the complete early blockage of folliculogenesis at the primary stage, with a high density of follicles of the prepubertal type. These results should prompt the reassessment of the role of gonadotropins in spermatogenesis, folliculogenesis and therapeutic applications in human hypogonadism and infertility.

Testicular Testosterone and Estradiol Concentrations and Aromatase Expression in Men with Nonobstructive Azoospermia

CONTEXT

Spermatogenesis is strictly regulated by the intratesticular hormonal milieu, in which testosterone (T) and estradiol (E2) play pivotal roles. However, the optimal expression of aromatase and intratesticular T (ITT) and E2 (ITE2) levels are unknown.

OBJECTIVE

To investigate ITT/ITE2 and aromatase expression in men with nonobstructive azoospermia (NOA) and to elucidate the roles of aromatase in spermatogenesis, as determined based on sperm retrieval by microdissection testicular sperm extraction (micro-TESE).

DESIGN AND SETTING

A retrospective study at a reproductive center using serum, testicular specimens, and intratesticular fluid.

PATIENTS

Seventy-six men with NOA, including 4 men who received 3 months of anastrozole administration prior to micro-TESE, and 18 men with obstructive azoospermia.

INTERVENTIONS

Testicular aromatase expression was evaluated using immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (RT-PCR). Intratesticular T and ITE2 levels were determined using liquid chromatography-tandem mass spectrometry.

RESULTS

Aromatase was mainly located in Leydig cells, and the levels of its transcript and protein expression levels were increased in men with NOA. No correlation was observed between serum T/E2 and ITT/ITE2 levels, whereas significant associations were observed between decreased ITT and increased ITE2, aromatase expression, and sperm retrieval. Treatment with anastrozole increased the ITT/ITE2 ratio and decreased aromatase expression.

CONCLUSIONS

A close association between the expression of aromatase in Leydig cells and ITT/ITE2 was shown. Leydig cell aromatase is a factor that is independently correlated with spermatogenesis, and aromatase inhibitors may open a therapeutic window by increasing ITT/ITE2 in selected patients.

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.

Hormonal Treatment of Men with Nonobstructive Azoospermia: What Does the Evidence Suggest?

Hormonal stimulation of spermatogenesis prior to surgery has been tested by some authors to maximize the sperm retrieval yield in patients with nonobstructive azoospermia. Although the rationale of such an approach is theoretically sound, studies have provided conflicting results, and there are unmet questions that need to be addressed. In the present narrative review, we reviewed the current knowledge about the hormonal control of spermatogenesis, the relationship between presurgical serum hormones levels and sperm retrieval rates, and the results of studies investigating the effect of hormonal treatments prior to microdissection testicular sperm extraction. We pooled the available data about sperm retrieval rate in patients with low vs. normal testosterone levels, and found that patients with normal testosterone levels had a significantly higher chance of successful sperm retrieval compared to those with subnormal T levels (OR 1.63, 95% CI 1.08–2.45, p = 0.02). These data suggest that hormonal treatment may be justified in patients with hypogonadism; on the other hand, the available evidence is insufficient to recommend hormonal therapy as standard clinical practice to improve the sperm retrieval rate in patients with nonobstructive azoospermia.

Adiposity is Associated with Decreased Serum 17-Hydroxyprogesterone Levels in Non-Diabetic Obese Men Aged 18-49: A Cross-Sectional Study

Obesity is associated with decreased circulating testosterone levels, the main male sex hormone. However, there are a number of different male sex hormones whose dynamics remain poorly understood regarding this pathology. In this regard, 17 hydroxyprogesterone (17-OH progesterone), as an important precursor of testosterone synthetized in testes and adrenal glands, could play an essential role in testosterone deficiency in male obesity. Moreover, similarly to testosterone, 17-OH progesterone could be closely associated with visceral fat distribution and metabolic dysfunction. Thus, the aim of this study was to assess serum 17-OH progesterone levels in non-diabetic obese young men and to evaluate their relationship with clinical, analytical, and anthropometric parameters. We conducted a cross-sectional study including 266 non-diabetic men with obesity (BMI ≥ 30 kg/m²) aged 18-49 years; 17-OH progesterone and total testosterone (TT) were determined by high-performance liquid chromatography mass spectrometry. 17-OH progesterone levels were significantly lower in tertile 3 of body fat percentage in comparison with tertile 1 (0.74 ng/mL vs. 0.94 ng/mL, p < 0.01; Bonferroni correction) and in comparison with tertile 2 (0.74 ng/mL vs. 0.89 ng/mL, p = 0.02; Bonferroni correction). 17-OH progesterone levels correlated negatively with weight, BMI, waist circumference, insulin, homeostatic model assessment of insulin resistance (HOMA-IR), and visceral fat, and positively with TT, free testosterone (FT), luteinizing hormone, and fat-free mass percentage. Multivariate linear-regression analysis showed that body fat percentage and HOMA-IR were inversely associated with 17-OH progesterone levels, while FT and ACTH were positively linked to circulating 17-OH progesterone levels. In conclusion, in a population of non-diabetic obese young men, 17-OH progesterone levels were inversely associated with adiposity. Body fat percentage and insulin resistance were negatively related to 17-OH progesterone levels, whereas FT and ACTH levels were positively associated with 17-OH progesterone levels.

Effects of acute hCG stimulation on serum INSL3 and 25-OH vitamin D in Klinefelter syndrome

BACKGROUND

It has recently been suggested that the hypergonadotropic hypogonadism characterizing Klinefelter syndrome (KS) might not be due to a steroidogenic dysfunction per se, but mainly to an altered testosterone (T) secretion into the bloodstream. However, the Leydig cell functionality remains incompletely studied in KS, and new markers should be considered. Previous data indicated that chronic hCG stimulation influences the production of both insulin-like peptide 3 (INSL3) and 25-hydroxy-vitamin D (25-VD) in eugonadal men.

AIM OF THE STUDY

To evaluate INSL3 and 25-VD serum levels, as markers of Leydig cell functionality, in association with sex steroids, after an acute hCG test in a group of KS patients and healthy volunteers.

METHODS

A retrospective analysis of a prospective case-control clinical trial was carried out. KS patients (n = 11) and age-matched healthy controls (n = 11) provided a basal blood sample (V0) immediately followed by a single intramuscular injection of hCG 5000 IU. Blood samples were taken in the following five days (V1-V5).

RESULTS

At baseline, INSL3 was lower in KS patients compared with controls (P = .007). When adjusted for INSL3 levels, the production of steroids was similar between KS patients and controls. 25-VD was in the insufficient range both in KS patients and in controls and was not different (P = .064). Acute hCG stimulation increased neither INSL3 nor 25-VD in both KS patients and controls. In controls, an inverse correlation was detected between INSL3 levels and body mass index (P = .020) and waist circumference (P = .020).

CONCLUSIONS

INSL3 secretion is independent from steroidogenesis, and its production is mostly not influenced by acute hCG stimulation both in KS men and in controls. INSL3 serum levels should be considered as a marker of Leydig cell differentiation and numbers rather than steroidogenesis. 25-VD serum levels are also not increased by a single acute hCG administration, which was not able to restore the normal concentrations of 25-VD.

Effect of Thyroxine Replacement on Leydig Cell and Sertoli Cell Function in Men with Hypothyroidism

CONTEXT

Thyroid hormones play an important role in reproductive and sexual function in both sexes. Comprehensive information on the ill-effects of hypothyroidism on Leydig cell, Sertoli cell and germ cell function is lacking in the existing literature.

AIMS

To investigate the effect of primary hypothyroidism and its treatment on testicular function - Sertoli cell, Leydig cells, seminal fluid and spermatozoa.

METHODS AND MATERIAL

This study was carried out as a descriptive study with a before-after study design in the endocrine department of a tertiary care hospital in South India. Forty treatment naïve, overtly primary hypothyroid, consenting male patients were included. Hormones assessed were free T3, free T4, thyroid stimulating hormone, follicle stimulating hormone [FSH], luteinizing hormone [LH], prolactin, testosterone, inhibin B[INHB], and insulin like factor 3[INSL3]. Semen analysis was done according to WHO 2010 guidelines in 37 subjects. Sexual function questionnaires like Androgen Deficiency in Aging Male [ADAM], and Arizona Sexual Experience Scale [ASEX] were used. After ensuring euthyroid state for consecutive 6 months with adequate dose of thyroxine sodium, reassessment of all parameters was done.

RESULTS

At baseline, 72.5 % had a low serum testosterone value (&lt; 230 ng/dl), 67.56 % had low total sperm motility, 72.97% had low total progressive sperm motility, 80% had low ADAM score and 72.72% had low ASEX score. A raised prolactin level was seen in 32.5% of study subjects. Hypogonadotropic hypogonadism was more common than hypergonadotropic hypogonadism (89.66% vs. 10.34%). On restoration of euthyroidism, all these parameters improved. Serum INSL3 and LH increased significantly after thyroxine replacement, unlike FSH and INHB.

CONCLUSIONS

Leydig cell function seemed more severely affected by hypothyroidism as compared to Sertoli cell function. Among sperm function parameters, motility was predominantly affected.

Can serum 17-hydroxyprogesterone and insulin-like factor 3 be used as a marker for evaluation of intratesticular testosterone?

Serum testosterone values vary considerably with little correlation to intratesticular testosterone (ITT). ITT is approximately ~100 times that of serum testosterone and is critical for spermatogenesis. Unfortunately, the only method to accurately measure ITT is invasive testicular aspiration and therefore is not performed routinely. The identification of a serum biomarker for ITT would allow serial monitoring during hormonal manipulation and the ability to assess the effectiveness of a male contraceptive agent. Prior studies have evaluated several serum biomarkers for their ability to accurately reflect ITT with data supporting 17-hydroxyprogesterone (17-OHP) and insulin-like factor 3 (INSL3) as a potential marker. Because evaluation of serum 17-OHP is readily available through commercial laboratories, in this review, we present the evidence for 17-OHP and how it can play a pivotal role in the management of male infertility.

Using 17-OHP as Serum Biomarker to Monitor Therapy in Patients With Hypogonadotropic Hypogonadism

Exogenous testosterone administration decreases intratesticular testosterone (ITT) significantly, an essential hormone for spermatogenesis. Therefore, treatment of patients with hypogonadotropic hypogonadism (HH) who desire infertility can be challenging. These patients are treated with recombinant follicle-stimulating hormone (FSH), clomiphene citrate, and human chorionic gonadotropin (hCG) to increase their ITT. However, there is no approved serum biomarker for ITT and it can only be measured via invasive testicular biopsy or aspiration. Previous authors have speculated that serum 17-hydroxyprogestrone (17-OHP) can be used as serum biomarker for ITT. In our case report, we demonstrate increase in 17-OHP associated with spermatogenesis after commencing treatment for infertility in patient with HH.

Development and validation of a mass spectrometry-based assay for quantification of insulin-like factor 3 in human serum

Background:

The circulating level of the peptide hormone insulin-like factor 3 (INSL3) is a promising diagnostic marker reflecting Leydig cell function in the male. Few commercial immunoassays of varying quality exist. Therefore, we decided to develop and validate a precise method for quantification of INSL3 by mass spectrometry.

Methods:

We developed an assay in which the INSL3 A-chain is released from the INSL3 A-B heterodimer by chemical reduction and alkylation. The alkylated INSL3 A-chain is quantitated by liquid chromatography-tandem mass spectrometry (LC-MS/MS), as substitute for serum INSL3. The method was compared to a validated and sensitive in-house serum INSL3 immunoassay using 97 serum samples from 12 healthy boys during pubertal transition. Adult levels were determined based on sera from 72 adult healthy males aged 18–40 years.

Results:

An LC-MS/MS assay with limit of detection and limit of quantification (LOQ) of 0.06 and 0.15 ng/mL, respectively, and intra-assay CVs <9% in the relevant ranges was obtained. The LC-MS/MS compared well with the in-house immunoassay (Deming regression slope: 1.28; Pearson correlation: R=0.86). INSL3 concentrations increased with pubertal maturation in healthy boys. INSL3 concentrations were above the LOQ in all samples from the adult men. The mean (±2 SD range)for serum INSL3 concentrations in the adult men was 2.2 (0.5–3.9) ng/mL.

Conclusions:

We have developed a robust and sensitive method suitable for quantitation of serum INSL3 in a clinical setting using LC-MS/MS instrumentation available in modern clinical laboratories. The method paves the way for future studies into the clinical role of serum INSL3 measurements.

New Biomarkers to Evaluate Hyperandrogenemic Women and Hypogonadal Men

Androgens can have variable effects on men and women. Women may be evaluated for androgen excess for several reasons. Typically, young premenopausal women present with clinical symptoms of hirsutism, alopecia, irregular menses, and/or infertility. The most common cause of these symptoms is polycystic ovary syndrome. After menopause, even though ovaries stop producing estrogen, they continue to produce androgen, and women can have new onset of hirsutism and alopecia. Laboratory evaluation involves measurement of the major ovarian and adrenal androgens. In women, age, phase of the menstrual cycle, menopausal status, obesity, metabolic health, and sex hormone-binding proteins significantly affect total-androgen levels and complicate interpretation. This review will summarize the clinically relevant evaluation of hyperandrogenemia at different life stages in women and highlight pitfalls associated with interpretation of commonly used hormone measurements. Hypogonadism in men is a clinical syndrome characterized by low testosterone and/or low sperm count. Symptoms of hypogonadism include decreased libido, erectile dysfunction, decreased vitality, decreased muscle mass, increased adiposity, depressed mood, osteopenia, and osteoporosis. Hypogonadism is a common disorder in aging men. Hypogonadism is observed rarely in young boys and adolescent men. Based on the defects in testes, hypothalamus, and/or pituitary glands, hypogonadism can be broadly classified as primary, secondary, and mixed hypogonadism. Diagnosis of hypogonadism in men is based on symptoms and laboratory measurement. Biomarkers in use/development for hypogonadism are classified as hormonal, Leydig and Sertoli cell function, semen, genetic/RNA, metabolic, microbiome, and muscle mass-related. These biomarkers are useful for diagnosis of hypogonadism, determination of the type of hypogonadism, identification of the underlying causes, and therapeutic assessment. Measurement of serum testosterone is usually the most important single diagnostic test for male hypogonadism. Patients with primary hypogonadism have low testosterone and increased luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Patients with secondary hypogonadism have low testosterone and low or inappropriately normal LH and FSH. This review provides an overview of hypogonadism in men and a detailed discussion of biomarkers currently in use and in development for diagnosis thereof.

Effects of multiple life stage exposure to the fungicide prochloraz in Xenopus laevis: Manifestations of antiandrogenic and other modes of toxicity

The Larval Amphibian Growth and Development Assay (LAGDA) is an internationally harmonized testing guideline for evaluating effects of chronic chemical exposure in amphibians. In order to evaluate the effects of chronic exposure to an antiandrogenic chemical in an amphibian model, prochloraz was tested using a variation of the LAGDA design. Exposure was initiated with <1d post-fertilization embryos at nominal concentrations of 0, 6.7, 20, 60 and 180 μg/L (0, 18, 53, 159, 478 nM) and continued in flow-through conditions until two months following the median time that controls completed metamorphosis. Growth, developmental rate, circulating thyroid hormone and thyroid gland histopathology were evaluated in a subsample at completion of metamorphosis. There were no effects on growth or development at this stage, but circulating thyroid hormone was elevated in the 20, 60 and 180 μg/L treatments and minimal to mild thyroid follicular cell hypertrophy was observed histologically in the 180 μg/L treatment. Growth, overt toxicity, and reproductive development were evaluated at test termination. There were no effects on growth in either gender, but livers and kidneys exhibited treatment-related pathologies consistent with organ toxicity related to metabolism and presumably impaired excretion of prochloraz metabolites. Histological assessments of female ovaries resulted in minimal pathologies only in the 180 μg/L treatment while male testes exhibited numerous treatment-related pathologies that are consistent with previously reported antiandrogenic effects of prochloraz in other species. The most severe testis pathologies occurred in the 180 μg/L treatment; however, incidences of treatment-related pathologies occurred in all prochloraz treatments. Müllerian duct regression in males was inhibited by prochloraz exposure while Müllerian duct maturation in females was accelerated, characteristic of a feminizing effect. Gene expression levels of potential biomarkers of testis function were also measured. Relative abundance of cyp17a1 transcripts was generally unaffected by prochloraz exposure whereas the Insl3 orthologue, rflcii, was elevated by 3 and >5-fold in the 60 and 180 μg/L treatments, respectively, indicating impaired Leydig cell maturation and testosterone signaling. Overall, prochloraz exposure caused effects characteristic of an antiandrogenic mode of action, which is consistent with previously reported results in other species and supports the utility of the LAGDA design for chemical testing.

Characterizing the reproductive transcriptomic correlates of acute dehydration in males in the desert-adapted rodent, Peromyscus eremicus

BACKGROUND

The understanding of genomic and physiological mechanisms related to how organisms living in extreme environments survive and reproduce is an outstanding question facing evolutionary and organismal biologists. One interesting example of adaptation is related to the survival of mammals in deserts, where extreme water limitation is common. Research on desert rodent adaptations has focused predominantly on adaptations related to surviving dehydration, while potential reproductive physiology adaptations for acute and chronic dehydration have been relatively neglected. This study aims to explore the reproductive consequences of acute dehydration by utilizing RNAseq data in the desert-specialized cactus mouse (Peromyscus eremicus).

RESULTS

We exposed 22 male cactus mice to either acute dehydration or control (fully hydrated) treatment conditions, quasimapped testes-derived reads to a cactus mouse testes transcriptome, and then evaluated patterns of differential transcript and gene expression. Following statistical evaluation with multiple analytical pipelines, nine genes were consistently differentially expressed between the hydrated and dehydrated mice. We hypothesized that male cactus mice would exhibit minimal reproductive responses to dehydration; therefore, this low number of differentially expressed genes between treatments aligns with current perceptions of this species' extreme desert specialization. However, these differentially expressed genes include Insulin-like 3 (Insl3), a regulator of male fertility and testes descent, as well as the solute carriers Slc45a3 and Slc38a5, which are membrane transport proteins that may facilitate osmoregulation.

CONCLUSIONS

These results suggest that in male cactus mice, acute dehydration may be linked to reproductive modulation via Insl3, but not through gene expression differences in the subset of other a priori tested reproductive hormones. Although water availability is a reproductive cue in desert-rodents exposed to chronic drought, potential reproductive modification via Insl3 in response to acute water-limitation is a result which is unexpected in an animal capable of surviving and successfully reproducing year-round without available external water sources. Indeed, this work highlights the critical need for integrative research that examines every facet of organismal adaptation, particularly in light of global climate change, which is predicted, amongst other things, to increase climate variability, thereby exposing desert animals more frequently to the acute drought conditions explored here.

Effects of long-acting GnRH antagonist, degarelix acetate, on plasma insulin-like peptide 3, testosterone and luteinizing hormone concentrations, and scrotal circumference in male goats

We recently reported that plasma insulin-like peptide 3 (INSL3) concentrations increased soon after endogenous and exogenous stimulations of LH in male goats and bulls. However, the effects of LH suppression on INSL3 secretion are unknown in domestic animals. Here, we examined the effects of a long-acting GnRH antagonist (degarelix acetate; 4 mg/kg) on the secretions of plasma INSL3 and testosterone in two phases, an immediate and a long-term phase in male goats (n = 6; aged, 13-16 months). During the immediate phase, blood was taken at 15-minute intervals for 8 hours on Days -5, 0, and 3. The GnRH antagonist was administered after 2-hour sampling of Day 0. Moreover, a daily blood sample was taken from Day 0 to Day 7, followed by twice a week until 9 weeks and finally at week 10. The scrotal circumference was recorded before treatment and continued biweekly until week 10. Concentrations of LH, INSL3, and testosterone in plasma were determined by EIA and the pulsatile nature of secretion analyzed using pulse XP software. The mean concentrations, pulse frequency (per hour), and pulse amplitude (peak-nadir) of plasma LH and testosterone reduced from pretreatment to posttreatment Day 0 and Day 3 (P < 0.05). A decline in mean concentrations, pulse frequency, and pulse amplitude of INSL3 was exhibited on posttreatment Day 3 compared with pretreatment (P < 0.01). During long-term sampling, a decline (P < 0.01) in plasma testosterone and INSL3 concentrations was observed 1 day after treatment and remained lower until 8.5 weeks after treatment, and thereafter returned to pretreatment levels. A reduction in scrotal circumference was recorded 4 weeks after treatment and remained lower until 10 weeks after treatment (P < 0.05). In conclusion, the acute regulation of INSL3 by LH was confirmed by reduction of plasma INSL3 levels within 3 days after GnRH antagonist treatment in male goats. Although the onset of suppression of testosterone was more rapid than that of INSL3, the low levels persisted for 8.5 weeks for both hormones, and subsequently the concentrations returned to pretreatment levels. A significant reduction in testicular size was also observed. The quick, long-lasting, and transient suppression of testosterone and INSL3 after a single injection implies a potential application of this antagonist in reversible long-term chemical castration in male goats.

Plasma insulin-like peptide 3 concentrations are acutely regulated by luteinizing hormone in pubertal Japanese Black beef bulls

Insulin-like peptide 3 (INSL3) is a major secretory product of testicular Leydig cells. The mechanism of acute regulation of INSL3 secretion is still unknown. The present study was undertaken in pubertal beef bulls to (1) determine the temporal relationship of pulsatile secretion among LH, INSL3, and testosterone and (2) monitor acute regulation of INSL3 secretion by LH using GnRH analogue and hCG. Blood samples were collected from Japanese Black beef bulls (N = 6) at 15-minute intervals for 8 hours. Moreover, blood samples were collected at -0.5, 0, 1, 2, 3, 4, 5, and 6 hours after GnRH treatment and -0.5, 0, 2, 4, and 8 hours on the day of treatment (Day 0), and Days 1, 2, 4, 8, and 12 after hCG treatment. Concentrations of LH, INSL3, and testosterone determined by EIAs indicated that secretion in the general circulation was pulsatile. The frequency of LH, INSL3, and testosterone pulses was 4.7 ± 0.9, 3.8 ± 0.2, and 1.0 ± 0.0, respectively, during the 8-hour period. Seventy percent of these INSL3 pulses peaked within 1 hour after a peak of an LH pulse had occurred. The mean increase (peak per basal concentration) of testosterone pulses was higher (P < 0.001) than that of INSL3 pulses. After GnRH treatment, LH concentrations increased (P < 0.01) dramatically 1 hour after treatment and remained high (P < 0.05) until the end of sampling, whereas an elevated (P < 0.05) INSL3 concentration occurred at 1, 2, 5, and 6 hours after treatment. Testosterone concentrations increased (P < 0.01) 1 hour after the treatment and remained high until the end of sampling. After hCG treatment, an increase of INSL3 concentration occurred at 2 and 4 hours, and Days 2, 4, and 8 after treatment (P < 0.05), whereas in case of testosterone, concentrations remained high (P < 0.01) until Day 8 after treatment. The increase (maximum per pretreatment concentration) of INSL3 concentrations after injecting GnRH or hCG was much lower (P < 0.001) than that of testosterone. In conclusion, secretion of INSL3 in blood of bulls occurred in a pulsatile manner. We inferred an acute regulation of INSL3 by LH in bulls because INSL3 concentrations increased immediately after endogenous and exogenous LH stimulation. The increase of INSL3 concentrations by LH was much lower than that of testosterone in bulls.

Identification of biochemical differences between different forms of male infertility by nuclear magnetic resonance (NMR) spectroscopy

PURPOSE

The aim of this study was to analyze the seminal plasma of patients with idiopathic/male factor infertility and healthy controls with proven fertility by NMR spectroscopy, with a hope of establishing difference in biomarker profiles, if any, between the groups.

METHODS

A total of 103 subjects visiting the infertility clinic of Manipal University with normozoospermic parameters, oligozoospermia, asthenozoospermia, azoospermia and teratozoospermia were included. Semen characteristics were analysed by standard criteria. Seminal plasma was subjected to NMR spectroscopy at a 700 MHz (1)H frequency. The resultant data was analyzed by appropriate software.

RESULTS

The analysis revealed significant differences between the fertile control group and other forms of male infertility. Interestingly, seminal plasma profile of the idiopathic infertility group showed distinct segregation from the control population as well as other infertile groups. The difference in biomarker profiles between the idiopathic infertility and the rest of the groups combined could originate from either the up-regulation or down regulation of a several compounds, including lysine, arginine, tyrosine, citrate, proline and fructose.

CONCLUSION

Our data suggests the presence of a metabolic reason behind the origin of idiopathic infertility. (1)H NMR based metabonomic profiling based on concentration of biomarker lysine has the potential to aid in the detection and diagnosis of idiopathic infertility in an efficient manner.

Serum levels of insulin-like factor 3, anti-Müllerian hormone, inhibin B, and testosterone during pubertal transition in healthy boys: a longitudinal pilot study

Insulin-like factor 3 (INSL3) is a promising marker of Leydig cell function with potentially high clinical relevance. Limited data of INSL3 levels in relation to other reproductive hormones in healthy pubertal boys exist. In this study, we aimed to evaluate longitudinal serum changes in INSL3 compared with LH, FSH, testosterone, inhibin B, and anti-Müllerian hormone (AMH) during puberty in healthy boys. Ten boys were included from the longitudinal part of the COPENHAGEN Puberty Study. Pubertal evaluation, including testicular volume, was performed and blood samples were drawn every 6 months for 5 years. Serum concentrations of testosterone were determined by a newly developed LC–MS/MS method, and serum concentrations of INSL3, AMH, inhibin B, FSH, and LH respectively were determined by validated immunoassays. The results showed that serum INSL3 levels increased progressively with increasing age, pubertal onset, and testicular volume. In six of the ten boys, LH increased before the first observed increase in INSL3. In the remaining four boys, the increase in LH and INSL3 was observed at the same examination. The increases in serum concentrations of LH, testosterone, and INSL3 were not parallel or in ordered succession and varied interindividually. We demonstrated that INSL3 concentrations were tightly associated with pubertal onset and increasing testicular volume. However, the pubertal increases in LH, INSL3, and testosterone concentrations were not entirely parallel, suggesting that INSL3 and testosterone may be regulated differently. Thus, we speculate that INSL3 provides additional information on Leydig cell differentiation and function during puberty compared with traditional markers of testicular function.

Insulin-like peptide 3 (INSL3) in men with congenital hypogonadotropic hypogonadism/Kallmann syndrome and effects of different modalities of hormonal treatment: a single-center study of 281 patients

CONTEXT

Insulin-like factor 3 (INSL3) is a testicular hormone secreted during fetal life, the neonatal period, and after puberty.

OBJECTIVE

To measure INSL3 levels in a large series of men with congenital hypogonadotropic hypogonadism (CHH)/ Kallmann syndrome (KS), in order to assess its diagnostic value and to investigate its regulation.

PATIENTS

We studied 281 CHH/KS patients (91 untreated, 96 receiving T, and 94 receiving combined gonadotropin therapy [human chorionic gonadotropin, hCG, and FSH]) and 72 age-matched healthy men.

METHODS

Serum INSL3 was immunoassayed with a validated RIA.

RESULTS

Mean (±SD) INSL3 levels (pg/mL) were 659 ± 279 in controls and lower (60 ± 43; P < .001) in untreated CHH/KS patients, with no overlap between the two groups, when the threshold of 250 pg/mL was used. Basal INSL3 levels were lower in both untreated CHH/KS men with cryptorchidism than in those with intrascrotal testes and in patients with testicular volumes below 4 mL. Significant positive correlations between INSL3 and both serum total T and LH levels were observed in untreated CHH/KS. Mean INSL3 levels remained low in T-treated CHH/KS patients and were significantly higher in men receiving combined hCG-FSH therapy (P < .001), but the increase was lower cryptorchid patients. FSH-hCG combination therapy or hCG monotherapy, contrary to T and FSH monotherapies, significantly increased INSL3 levels in CHH/KS.

CONCLUSIONS

INSL3 is as sensitive a marker as T for the evaluation of altered Leydig cell function in CHH/KS patients. INSL3 levels correlate with LH levels in CHH/KS men showing, together with the rise in INSL3 levels during hCG therapy, that INSL3 secretion seems not constitutively secreted during adulthood but is dependence on pituitary LH.

The use of genomics, proteomics, and metabolomics in identifying biomarkers of male infertility

Although male factors account for approximately 50% of all infertility, the mechanisms underlying their origin are unknown. Currently, clinicians rely primarily on semen analyses to predict male reproductive potential and chart treatment success. Even when invasive procedures are performed, the causes of male factor infertility frequently remain elusive. Recently, the advent of new technologies has spurred the search for novel male infertility biomarkers, and the detection of genes, proteins, or metabolites unique to the infertile male holds much promise. The concept that a cost-effective, noninvasive, and accurate set of biomarkers can be identified to diagnose male factor infertility is tantalizing. This review focuses on the various methodologies used in the discovery of novel biomarkers along with their findings. Specific attention is paid to recent advances in the fields of genetics, proteomics, and metabolomics.