The Role of Anti-Müllerian Hormone in Ovarian Function

Anti-Müllerian hormone (AMH) is a member of the transforming growth factor β (TGFβ) superfamily, whose actions are restricted to the endocrine-reproductive system. Initially known for its role in male sex differentiation, AMH plays a role in the ovary, acting as a gatekeeper in folliculogenesis by regulating the rate of recruitment and growth of follicles. In the ovary, AMH is predominantly expressed by granulosa cells of preantral and antral follicles (i.e., post primordial follicle recruitment and prior to follicle-stimulating hormone (FSH) selection). AMH signals through a BMP-like signaling pathway in a manner distinct from other TGFβ family members. In this review, the latest insights in AMH processing, signaling, its regulation of spatial and temporal expression pattern, and functioning in folliculogenesis are summarized. In addition, effects of AMH variants on ovarian function are reviewed.

AMH and other markers of ovarian function in patients with Turner syndrome - a single center experience of transition from pediatric to gynecological follow up

Turner syndrome (TS) is a chromosomal disorder that affects about 1 in 2500 female births and is characterized by the partial or complete absence of the second X chromosome. Depending on karyotype, TS is associated with primary ovarian insufficiency (POI). Approximately 50% of girls with a mosaic 45, X/46, XX karyotype may enter puberty spontaneously, but only 5-10% of women with TS achieve pregnancy without egg donation. In this review, we will evaluate the clinical use of markers of ovarian function in TS patients. Based on longitudinal studies of serum concentrations of reproductive hormones as well as ovarian morphology in healthy females and patients with TS, we will evaluate how they can be applied in a clinical setting. This is important when counseling patients and their families about future ovarian function essential for pubertal development and fertility. Furthermore, we will report on 20 years of experience of transition from pediatric to gynecological and adult endocrinological care in our center at Rigshospitalet, Copenhagen, Denmark.

Modeling Human Gonad Development in Organoids

BACKGROUND

Our learning about human reproductive development is greatly hampered due to the absence of an adequate model. Animal studies cannot truthfully recapitulate human developmental processes, and studies of human fetal tissues are limited by their availability and ethical restrictions. Innovative three-dimensional (3D) organoid technology utilizing human pluripotent stem cells (hPSCs) offered a new approach to study tissue and organ development in vitro. However, a system for modeling human gonad development has not been established, thus, limiting our ability to study causes of infertility.

METHODS

In our study we utilized the 3D hPSC organoid culture in mini-spin bioreactors. Relying on intrinsic self-organizing and differentiation capabilities of stem cells, we explored whether organoids could mimic the development of human embryonic and fetal gonad.

RESULTS

We have developed a simple, bioreactor-based organoid system for modeling early human gonad development. Male hPSC-derived organoids follow the embryonic gonad developmental trajectory and differentiate into multipotent progenitors, which further specialize into testicular supporting and interstitial cells. We demonstrated functional activity of the generated cell types by analyzing the expression of cell type-specific markers. Furthermore, the specification of gonadal progenitors in organoid culture was accompanied by the characteristic architectural tissue organization.

CONCLUSION

This organoid system opens the opportunity for detailed studies of human gonad and germ cell development that can advance our understanding of sex development disorders. Implementation of human gonad organoid technology could be extended to modeling causes of infertility and regenerative medicine applications.

Anti-Müllerian Hormone in Female Reproduction

Anti-Müllerian hormone (AMH), also called Müllerian inhibiting substance, was shown to be synthesized by the ovary in the 1980s. This article reviews the main findings of the past 20 years on the regulation of the expression of AMH and its specific receptor AMHR2 by granulosa cells, the mechanism of action of AMH, the different roles it plays in the reproductive organs, its clinical utility, and its involvement in the principal pathological conditions affecting women. The findings in respect of regulation tell us that AMH and AMHR2 expression is mainly regulated by bone morphogenetic proteins, gonadotropins, and estrogens. It has now been established that AMH regulates the different steps of folliculogenesis and that it has neuroendocrine effects. On the other hand, the importance of serum AMH as a reliable marker of ovarian reserve and as a useful tool in the prediction of the polycystic ovary syndrome (PCOS) and primary ovarian failure has also been acknowledged. Last but not least, a large body of evidence points to the involvement of AMH in the pathogenesis of PCOS.

High Variability of Molecular Isoforms of AMH in Follicular Fluid and Granulosa Cells From Human Small Antral Follicles

Anti-Müllerian hormone (AMH) is a member of the TGF-β superfamily produced by follicular granulosa cells (GCs) in women from late gestation to the end of reproductive life. AMH is thought to inhibit aromatase (i.e., CYP19) expression and decrease the conversion of androgens to oestrogens, especially in small antral follicles before dominance is achieved. Thus, AMH acts as a gatekeeper of ovarian steroidogenesis. However, the exact function and processing of AMH has not been fully elucidated. The present study measured and determined AMH isoforms in human follicular fluid (FF) from small antral follicles and in human GCs using four ELISAs, western blot, and immunofluorescence analysis. We evaluated the presence of the following isoforms: full-length AMH precursor (proAMH), cleaved associated AMH (AMH_N,C), N-terminal pro-region (AMH_N), and active C-terminal (AMH_C) AMH. A negative correlation between follicle diameter and the AMH forms was detected. Moreover, western blot analysis detected various AMH forms in both FFs and GCs, which did not match our consensus forms, suggesting an unknown proteolytic processing of AMH. The presence of these new molecular weight isoforms of AMH differs between individual follicles of identical size in the same woman. This study detected several AMH forms in FF and GCs obtained from human small antral follicles, which suggests that intrafollicular processing of AMH is complex and variable. Thus, it may be difficult to develop an antibody-based AMH assay that detects all AMH isoforms. Furthermore, the variability between follicles suggests that designing a recombinant AMH standard will be difficult.

Anti-Müllerian hormone is expressed and secreted by bovine oviductal and endometrial epithelial cells

In this study, we investigated whether bovine oviducts and endometria produce anti-Müllerian hormone (AMH) (for paracrine and autocrine signaling). Reverse transcription-polymerase chain reaction and western blotting detected AMH expression in oviductal and endometrial specimens. Immunohistochemistry revealed robust AMH expression in the ampulla and isthmus epithelia, and the glandular and luminal endometrial epithelia (caruncular endometria). AMH mRNA (measured by real-time PCR) and protein expression in these layers did not significantly differ among estrous phases in adult Japanese Black (JB) heifers (p > .1). Furthermore, the expression in these layers also did not differ among Holstein cows (93.8 ± 5.8 months old), JB heifers (25.5 ± 0.4 months old), and JB cows (97.9 ± 7.9 months old). We also compared AMH concentrations in the oviduct and uterine horn fluids among the three groups (measured by immunoassays). Interestingly, the AMH concentration in the oviduct fluid, but not in the uterine horn fluid, of Holstein cows was lower than those in JB heifers and cows (p < .05). Therefore, bovine oviducts and endometria express AMH and likely secrete it into the oviduct and uterine fluids.

Anti-Müllerian hormone and its receptor are detected in most gonadotropin-releasing-hormone cell bodies and fibers in heifer brains

Circulating concentrations of Anti-Müllerian hormone (AMH) can indicate fertility in various animals, but the physiological mechanisms underlying the effect of AMH on fertility remain unknown. We recently discovered that AMH has extragonadal functions via its main receptor, AMH receptor type 2 (AMHR2). Specifically, AMH stimulates the secretion of luteinizing hormone and follicle-stimulating hormone from bovine gonadotrophs. Moreover, gonadotrophs themselves express AMH to exert paracrine/autocrine functions, and AMH can activate gonadotropin-releasing-hormone (GnRH) neurons in mice. This study aimed to evaluate whether AMH and AMHR2 are detected in areas of the brain relevant to neuroendocrine control of reproduction: the preoptic area (POA), arcuate nucleus (ARC), and median eminence (ME), and in particular within GnRH neurons. Reverse transcription-polymerase chain reaction detected both AMH and AMHR2 mRNA in tissues containing POA, as well as in those containing both ARC and ME, collected from postpubertal heifers. Western blotting detected AMH and AMHR2 protein in the collected tissues. Triple fluorescence immunohistochemistry revealed that most cell bodies or fibers of GnRH neurons were AMHR2-positive and AMH-positive, although some were negative. Immunohistochemistry revealed that 75% to 85% of cell bodies and fibers of GnRH neurons were positive for both AMH and AMHR2 in the POA, ARC, and both the internal and external zones of the ME. The cell bodies of GnRH neurons were situated around other AMH-positive cell bodies or fibers of GnRH and non-GNRH neurons. Our findings thus indicate that AMH and AMHR2 are detected in most cell bodies or fibers of GnRH neurons in the POA, ARC, and ME of heifer brains. These data support the need for further study as to how AMH and AMHR2 act within the hypothalamus to influence GnRH and gonadotropin secretion.

Adjusting antimüllerian hormone levels for age and body mass index improves detection of polycystic ovary syndrome

OBJECTIVE

To examine whether accounting for a woman's age and body mass index (BMI) would improve the ability of antimüllerian hormone (AMH) to distinguish between women with (cases) and without (controls) polycystic ovarian syndrome (PCOS).

DESIGN

An opportunistic case-control dataset of reproductive age women having evaluations for PCOS as defined by National Institutes of Health criteria.

SETTING

Two medical centers in the United States enrolled women. Serum samples were analyzed for relevant analytes.

PATIENTS

Women were between 18 and 39 years of age when samples and clinical information were collected. Residual samples had been stored for 2-17 years. AMH was measured via immunoassay.

INTERVENTIONS

None; this was an observational study.

MAIN OUTCOME MEASURES

Detection and false-positive rates for PCOS were computed for AMH results expressed as multiples of the median (MoM) both before and after adjustment for the woman's age and BMI.

RESULTS

Using unadjusted AMH MoM results, 168 cases (78%) cases were at or beyond the 90^th centile of controls (2.47 MoM). After accounting for each woman's age and BMI, 188 (87%) of those women were beyond the 90^th centile of controls (2.20 MoM), a significant increase (P = .015). The adjusted AMH MoM levels fitted logarithmic normal distributions well (mean, standard deviation for controls and cases of 0.0000, 0.2765 and 0.6884, 0.2874, respectively) and this allowed for computation of patient-specific PCOS risks.

CONCLUSIONS

Accounting for the woman's age and BMI resulted in significantly higher AMH-based detection rates for PCOS at a 10% false-positive rate, and patient-specific PCOS risks could be computed.

Investigation of soluble anti-Müllerian hormone receptor type 2 as a biomarker for diagnosis of female fertility disorders

RESEARCH QUESTION

The ectodomain of the anti-Müllerian hormone (AMH) type 2 receptor is shed by proteases under certain conditions, which makes it measurable in the blood. The aim of this study was to identify correlations of soluble anti-Müllerian hormone receptor type 2 (sAMHR2) with other sex hormone concentrations and to assess whether sAMHR2 may serve as a new biomarker in fertility disorders.

DESIGN

In a retrospective cross-sectional study of women (n = 186) with different gynaecological-endocrinological disorders, mixed-effect models were used to analyse the correlation with established diagnostic hormone tests. Receiver operating characteristic curve analysis was performed to assess the diagnostic performance.

RESULTS

There was a strong correlation of sAMHR2 with LH (r = 0.898) and FSH (r = 0.846) and a moderate correlation of AMH with testosterone (r = 0.666) and androstenedione (r = 0.696) (all P < 0.001). In diagnoses of polycystic ovary syndrome (PCOS), AMH showed the best performance (area under the curve [AUC] 0.981, cut-off 4 ng/ml) with 96% sensitivity and 94% specificity. sAMHR2 concentrations and sAMHR2/AMH ratios were elevated in women with ovarian insufficiency, compared with all other study groups, including post-menopausal women on hormone replacement therapy. Highest sensitivity and specificity (100% and 98.2%, respectively) were achieved with sAMHR2/AMH ratio for the diagnosis of post-menopausal status (cut-off 68.85). The sAMHR2/AMH ratio (AUC 0.997) had a better performance than sAMHR2 (AUC 0.947), FSH (AUC 0.989) and LH (AUC 0.967).

CONCLUSIONS

The sAMHR2/AMH ratio may serve as a useful biomarker for infertility diagnostics to identify post-menopausal women.

Defective AMH signaling disrupts GnRH neuron development and function and contributes to hypogonadotropic hypogonadism

Congenital hypogonadotropic hypogonadism (CHH) is a condition characterized by absent puberty and infertility due to gonadotropin releasing hormone (GnRH) deficiency, which is often associated with anosmia (Kallmann syndrome, KS). We identified loss-of-function heterozygous mutations in anti-Müllerian hormone (AMH) and its receptor, AMHR2, in 3% of CHH probands using whole-exome sequencing. We showed that during embryonic development, AMH is expressed in migratory GnRH neurons in both mouse and human fetuses and unconvered a novel function of AMH as a pro-motility factor for GnRH neurons. Pathohistological analysis of Amhr2-deficient mice showed abnormal development of the peripheral olfactory system and defective embryonic migration of the neuroendocrine GnRH cells to the basal forebrain, which results in reduced fertility in adults. Our findings highlight a novel role for AMH in the development and function of GnRH neurons and indicate that AMH signaling insufficiency contributes to the pathogenesis of CHH in humans.

Characterization of follicles in girls and young women with Turner syndrome who underwent ovarian tissue cryopreservation

OBJECTIVE

To characterize ovarian follicles of girls and young women with Turner syndrome (TS) who underwent ovarian tissue cryopreservation (OTC).

DESIGN

Retrospective case-control study.

SETTING

University hospital.

PATIENT(S)

Fifteen girls and young women with TS aged 5-22 years at OTC were included, together with 42 control girls and young women aged 1-25 years who underwent OTC because of cancer.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Follicle density (follicles/mm³), morphology, and health were assessed in ovarian cortex biopsies from TS patients and compared with controls. Hormone concentrations were measured in serum and follicle fluids. Immature cumulus oocyte complexes were obtained and matured in vitro.

RESULT(S)

Follicles were found in 60% of the biopsies (9 of 15) from TS ovaries. In 78% of the ovaries (7 of 9) with follicles, the follicle density was within the 95% confidence interval of the control group. There was a high rate of abnormal follicle morphology. Six follicle-specific proteins were expressed similarly in TS and control ovaries. However, apoptosis and zona pellucida protein expression were found to be abnormal in TS. Turner syndrome follicle fluid from small antral follicles had lower concentrations of estrogen and testosterone and higher concentrations of antimüllerian hormone than controls. Thirty-one cumulus oocyte complexes were collected from one patient and cultured for 48 hours in vitro, resulting in five metaphase II oocytes (maturation rate 16%, degeneration rate 19%).

CONCLUSION(S)

The benefits of OTC may be limited to a highly selected group of TS mosaic patients in whom a sizeable pool of normal follicles is present at OTC.

Bovine gonadotrophs express anti-Müllerian hormone (AMH): comparison of AMH mRNA and protein expression levels between old Holsteins and young and old Japanese Black females

Anti-Müllerian hormone (AMH) is secreted from ovaries and stimulates gonadotrophin secretion from bovine gonadotroph cells. Other important hormones for endocrinological gonadotroph regulation (e.g. gonadotrophin-releasing hormone, inhibin and activin) have paracrine and autocrine roles. Therefore, in this study, AMH expression in bovine gonadotroph cells and the relationships between AMH expression in the bovine anterior pituitary (AP) and oestrous stage, age and breed were evaluated. AMH mRNA expression was detected in APs of postpubertal heifers (26 months old) by reverse transcription-polymerase chain reaction. Based on western blotting using an antibody to mature C-terminal AMH, AMH protein expression was detected in APs. Immunofluorescence microscopy utilising the same antibody indicated that AMH is expressed in gonadotrophs. The expression of AMH mRNA and protein in APs did not differ between oestrous phases (P&gt;0.1). We compared expression levels between old Holsteins (79.2±10.3 months old) and young (25.9±0.6 months old) and old Japanese Black females (89.7±20.3 months old). The APs of old Holsteins exhibited lower AMH mRNA levels (P&lt;0.05) but higher AMH protein levels than those of young Japanese Black females (P&lt;0.05). In conclusion, bovine gonadotrophs express AMH and this AMH expression may be breed-dependent.

Müllerian inhibiting substance/anti-Müllerian hormone as a fertility preservation agent

PURPOSE OF REVIEW

The nascent field of oncofertility is quickly gaining traction as novel experimental treatments are being developed, driving a renewed interest in Müllerian inhibiting substance (MIS) as an ovarian fertoprotectant.

RECENT FINDINGS

MIS is unique in its mechanisms of ovarian protection by virtue of acting directly on granulosa cells of primordial follicles and for being a benign reproductive hormone, with few side effects. We will explore in this review how it may be utilized to protect the ovary from chemotherapy, or to enhance ovarian tissue cryopreservation therapy. We will also examine potential mechanisms of action of MIS across multiple cell types, as well as current limitations in our understanding of the pharmacology of recombinant MIS.

SUMMARY

The usefulness of MIS as a fertoprotectant may be dependent on the mechanisms of gonadotoxicity of each chemotherapeutic. Further investigation is needed to determine how to best deliver and combine MIS treatment to existing fertility management strategies.

The AMH genotype (rs10407022 T>G) is associated with circulating AMH levels in boys, but not in girls

OBJECTIVE

Fetal anti-Müllerian hormone (AMH) is responsible for normal male sexual differentiation, and circulating AMH is used as a marker of testicular tissue in newborns with disorders of sex development. Little is known about the mechanism of action in postnatal life. A recent genome wide association study (GWAS) reported genetic variation of AMH affecting AMH levels in young men. This study investigated the effect of genetic variation of AMH and AMH type II receptor (AMHR2) (AMHrs10407022 T>G and AMHR2rs11170547 C>T) on circulating reproductive hormone levels and pubertal onset in boys and girls.

DESIGN AND METHODS

This study is a combined longitudinal and cross-sectional study in healthy Danish boys and girls from the general population. We included 658 boys aged 5.8-19.8 years and 320 girls aged 5.6-16.5 years. The main outcome measures were genotyping of AMH and AMHR2, pubertal staging and serum levels of reproductive hormones.

RESULTS

AMHrs10407022T>G was associated with higher serum levels of AMH in prepubertal boys (TT: 575 pmol/L vs TG: 633 pmol/L vs GG: 837 pmol/L, P = 0.002) and adolescents (TT: 44 pmol/L vs TG: 58 pmol/L vs GG: 79 pmol/L, P < 0.001). Adolescent boys carrying the genetic variation also had lower levels of LH (TT: 3.0 IU/L vs TG: 2.8 IU/L vs GG: 1.8 IU/L, P = 0.012). Hormone levels in girls and pubertal onset in either sex did not seem to be profoundly affected by the genotypes.

CONCLUSION

Our findings support recent GWAS results in young adults and expand our understanding of genetic variation affecting AMH levels even in boys prior to the pubertal decline of circulating AMH.

The Impact of the Biological Variability or Assay Performance on AMH Measurements: A Prospective Cohort Study With AMH Tested on Three Analytical Assay-Platforms

This study examined longitudinal, age-related and intra-individual variation in Anti-Müllerian Hormone (AMH) in regular menstruating women and correlated the hormonal levels to the antral follicle count (AFC). The impact of variations on an algorithm for calculation of follitropin-dose for ovarian stimulation were also tested. The study was carried out at a fertility clinic of a tertiary university hospital and had a prospective trial design. Twenty-six healthy women not receiving infertility treatment aged 22 to 50 years participated. Blood sampling for hormonal analysis was done every fifth day throughout three consecutive menstrual cycles, AFC was determined with 3-dimentional ultrasound and AMH measured by different assays from Beckman Coulter, Roche and Ansh Labs. Outcome measures were maximum and minimum difference in absolute and relative terms for each study subject during the test-period, coefficient of variation (Cv) for AMH for each cycle and cycle-day and correlation between AMH and AFC. The impact from variable AMH levels on an algorithm calculating follitrophin-delta dose in ovarian stimulation was explored. A significant longitudinal age-independent variation in AMH-levels and coefficient of variation in cycles and cycle days was found. A strong correlation between AMH-levels and AFC was confirmed and a case of significant divergence between assays was seen. Variations in AMH had a significant impact on an algorithm calculated dosage of gonadotrophins in ovarian stimulation. The finding of a substantial longitudinal variation in AMH question one recording being sufficient in quantifying gonadotrophins for ovarian stimulation, decision making and prognostication related to infertility treatment and counseling. Occasionally, commercial assays may fail to recognize specific AMH cleavage-products.

A quantitative comparison of anti-Müllerian hormone measurement and its shifting boundaries between two assays

OBJECTIVE

Anti-Müllerian hormone (AMH), a quantitative marker of ovarian reserve, is used for both clinical and research purposes in the field of reproductive medicine. Numerous AMH assays have been developed. Among other factors, the lack of large-scale comparisons of the various assays hinders the universal interpretation of AMH levels. Moreover, little is known of the practical performance of highly sensitive assays compared with conventional assays with regard to the very low AMH levels found in women nearing menopause. This study aimed to compare the measurements of the Gen II (Beckman Coulter) assay with those of the highly sensitive picoAMH (AnshLabs) assay.

METHODS

This cross-sectional study included 1985 premenopausal women who completed the second visit of the population-based Doetinchem Cohort Study, with a mean age of 42±7years. AMH levels were measured with the Gen II and picoAMH assays. Passing-Bablok and Bland Altman analyses were performed and differences in the proportion of detectable samples were assessed.

RESULTS

The results from the Gen II and picoAMH assays were highly correlated, with a Spearman correlation coefficient of 0.91. The Passing-Bablok regression formula was picoAMH=0.01+1.69*GenII, meaning that on average picoAMH levels were 69% higher than Gen II levels. Of the 670 samples with an undetectable AMH value with the Gen II assay, AMH could be detected in 78% with the picoAMH assay, at a median concentration [interquartile range] of 0.05 [0.01-0.14] ng/mL.

CONCLUSION

These results indicate that, despite a high correlation, there is a large relative difference between results of the Gen II and picoAMH assays. The use of a highly sensitive AMH assay is likely to result in a large increase in the proportion of samples with detectable levels. This may enable research into women's health across the menopausal transition and research into the potential clinical benefits of distinguishing between women with very low ovarian reserve.