Ian. S. McLennan

Anti-Müllerian hormone (AMH) is a paracrine regulator of ovarian follicles. Vitamin D (Vit D) regulates AMH production in vitro, but its role as a regulator of ovarian AMH production is contentious. If Vit D influences ovarian AMH production, then an acute rise in Vit D level should lead to an acute rise in circulating AMH levels. This hypothesis was tested with a randomized double-blind design, with 18–25-year-old women recruited from the community. The study was conducted in early spring, when the marker of Vit D level (25-hydroxyvitamin D, 25(OH)D) tends to be at its nadir. The women consumed either an oral dose of 50,000 IU of Vit D3 (n = 27) or placebo (n = 22). The initial 25(OH)D ± SD value was 53.6 ± 23.3 nmol/L, with 42 of the 49 women having a value below 75 nmol/L, consistent with seasonal nadir. All women receiving Vit D3 treatment exhibited a robust increase in serum 25(OH)D within 1 day (15.8 ± 1.1 nmol/L (n = 27), p < 0.0001), with the increase sustained over the study week. Circulating levels of AMH in the women receiving Vit D3 progressively rose during the following week, with a mean increase of 12.9 ± 3.7% (n = 24, p = 0.001). The study supports the hypothesis that Vit D’s positive effects on the fertility of woman may involve the regulation of ovarian AMH levels.

Purpose High levels of circulating anti-Müllerian hormone are unique to developing males, but the function of anti-Müllerian hormone in boys is unknown. In mice, anti-Müllerian hormone contributes to the male biases in the brain, but its receptors are present throughout non-sexually dimorphic portions of the brain. In humans, the speed of maturation is the most overt difference between girls and boys. We postulate that this is because anti-Müllerian hormone slows the maturation of the male human brain. Methods One hundred and fourty three 5-year or 6-year-old boys and 38 age-matched girls drew a person and donated a blood sample. The children’s drawings were blind-scored to generate a maturity index. The level of anti-Müllerian hormone and the other Sertoli cell hormone, inhibin B, were measured by ELISA. The relationship between the children’s age, hormones and maturity index were examined by linear regression analysis. Results The girls drew more complex and realistic person than the boys (32%, p = 0.001), with their drawings also being larger (39%, p = 0.037) and more coloured-in (235%, p = 0.0005). The maturity index in boys correlated with age (+r = 0.43, p < 0.0005) and anti-Müllerian hormone level (−r = −0.29, p < 0.0005). The association between maturity index and anti-Müllerian hormone level persisted when corrected for age and for inhibin B (r = −0.24, p = 0.0005). The calculated effect of the median level of anti-Müllerian hormone (1 nM) was equal to 0.81 months of development. The size and colouring of the drawings did not correlate with the boys’ age, anti-Müllerian hormone or inhibin B. Conclusions This exploratory study provides the first indicative evidence that circulating anti-Müllerian hormone may influence the development of the human brain.

The hypothesis that, in contrast to other transforming growth factor‐beta (TGFβ) superfamily ligands, the dose–response curve of Anti‐Müllerian hormone (AMH) is unmodulated was tested by examining whether known TGFB superfamily modulators affect AMH signaling, using a P19/BRE luciferase reporter assay. AMH_C and AMH_N,C activated the reporter with an EC50 of approximately 0.5 nM. Follistatins (FS) produced concentration‐dependent increases in AMH_C‐ and AMH_N,C‐initiated reporter activity, with FS288 being more potent than FS315; however, the maximum bioactivity of AMH was not altered by either follistatin. Thirteen other TGFβ regulators (Chordin, Chordin‐like 1, Chordin‐like 2, Differential screening‐selected gene aberrative in neuroblastoma [DAN], Decorin, Endoglin, Follistatin‐like 1, Follistatin‐like 3, Follistatin‐like 4, Noggin, α2 macroglobulin, TGFβ receptor 3, Von Willebrand factor C domain‐containing 2) had little or no effect. Surface plasmon resonance analysis showed no significant association between FS288 and AMH_C, suggesting that FS288 indirectly regulates AMH signaling. Activin A, a direct target of FS288, did not itself induce reporter activity in P19 cells, but did prevent the FS288‐induced increase in AMH signaling. Hence, local concentrations of FS288 and Activin A may influence the response of some cell types to AMH.

Anti-Müllerian hormone (AMH) is an atypical hormone, as its circulating levels are predominantly determined by size of the endocrine gland (i.e. number and type of ovarian follicles). Thus, ovarian reserve is the dominant influence on circulating levels of AMH, accounting for 55~75% of the variance in this hormone in premenopausal women ( Fanchin et al., 2003; Hansen et al., 2011; Bentzen et al., 2013). The lesser determinants of AMH levels are incompletely known, and are the subject of current controversy, arising from differences in methodology. When studies involve repeated measurement from the same individual, then circulating AMH levels appear to be influenced by the ovarian cycle ( Hadlow et al., 2013), pregnancy ( Nelson et al., 2010; Koninger et al., 2013; Hamilton et al., 2016; Pankhurst et al., 2016b) and vitamin D status ( Dennis et al., 2012). In contrast, when the study group involves either a single AMH value per women or averaged AMH values from multiple women, variable conclusions have been reached, with negative findings being commonly reported for pregnancy ( La Marca et al., 2005; Lutterodt et al., 2009) and vitamin D status, both previously ( Chang et al., 2014; Pearce et al., 2015; Neville et al., 2016) and now ( Drakopoulos et al., 2016) in this issue. In some instances, the negative results generated are false, leading to controversy within the literature. This commentary discusses the circumstances when methodological issues arise in AMH research and gives examples of robust, efficient alternative methodologies.

Circulating Anti-Müllerian hormone (AMH) is derived from the gonads, and is a mixture of the prohormone (proAMH), which does not bind to AMH receptors, and receptor-competent AMH. The functions of a hormone are partially defined by the factors that control its levels. Ovarian reserve accounts for 55~75% of the woman-to-woman variation in AMH level, leaving over 25% of the biological variation to be explained. Pregnancy has been reported to decrease circulating AMH levels, but the observations are inconsistent, with the effect of pregnancy on the bioactivity of AMH being unknown. We have therefore undertaken a longitudinal study of circulating proAMH and total AMH during pregnancy. Serum samples were drawn at 6–8 gestational time-points (first trimester to post-partum) from 25 healthy women with prior uneventful pregnancies. The total AMH and proAMH levels were measured at each time-point using ELISA. The level of circulating total AMH progressively decreased during pregnancy, in all women (p<0.001). On average, the percentage decline between the first trimester and 36–39 weeks’ gestation was 61.5%, with a standard deviation of 13.0% (range 30.4–81.2%). The percentage decline in total AMH levels associated with maternal age (R = -0.53, p = 0.024), but not with the women’s first trimester AMH level. The postpartum total AMH levels showed no consistent relationship to the woman’s first trimester values (range 31–273%). This raises the possibility that a fundamental determinant of circulating AMH levels is reset during pregnancy. The ratio of proAMH to total AMH levels exhibited little or no variation during pregnancy, indicating that the control of the cleavage/activation of AMH is distinct from the mechanisms that control the total level of AMH.

Anti‐Müllerian hormone (AMH) is a gonadal hormone, which induces aspects of the male phenotype, and influences ovarian follicular recruitment. AMH is synthesized as a proprotein (proAMH), which is incompletely cleaved to the receptor‐competent AMH_N,C. AMH ELISAs have not distinguished between proAMH and AMH_N,C; consequently, the physiological ranges of circulating proAMH and AMH_N,C are unknown. A novel proAMH ELISA has been used to assay serum proAMH in humans. Total AMH was also measured, enabling the AMH_N,C concentration to be calculated. Stored serum from 131 boys, 80 younger, and 106 older men were examined, with serum from 14 girls and 18 women included for comparison. The mean levels of proAMH and AMH_N,C in pM were respectively: boys (253, 526), men (7.7, 36), elderly men (5.7, 19), girls (3.3, 15), and women (5.2, 27) (boys vs. men, P < 0.001; girls vs. women, P = 0.032). The proportion of proAMH as a percentage of total AMH (API) was approximately twofold higher in boys than men (P < 0.001) with little overlap between the ranges, with girls also exhibiting lesser cleavage of their AMH than women (P < 0.001). The API varied within each population group. In young men, the API did not correlate with circulating levels of the other testicular hormones (testosterone, InhB, and INSL3). In conclusion, the cleavage of circulating AMH varies extensively within the human population, with most individuals having significant levels of proAMH. The physiological and clinical relevance of circulating proAMH needs to be established.

This work was funded by a grant from the Health Research Council of New Zealand (14–441).

The testes secrete four hormones (anti-Müllerian hormone, insulin-like peptide 3, Inhibin B and testosterone) from two endocrine cell types. It is unknown whether anti-Müllerian hormone and insulin-like peptide 3 levels have a diurnal variation, and if so, whether they covary during the day with testosterone and InhB. Sera were obtained from 13 men at 00:00, 06:00, 09:00, 12:00, 14:00, 17:00 and 19:00 hours and the levels of their testicular hormones measured by ELISA. A second cohort of 20 men was similarly examined with blood drawn at 19:00 and the following 06:00. Anti-Müllerian hormone levels exhibited a subtle diurnal pattern with a 19:00 peak that was 4.9% higher on average than the 06:00 nadir (p = 0.004). The decrease in anti-Müllerian hormone coincided with a rise in testosterone and InhB, but there was no association between the person-to-person variation in the diurnal patterns of anti-Müllerian hormone and testosterone or Inhibin B. Insulin-like peptide 3 had no diurnal pattern, with only minor sporadic variation between time points being observed in some men. In conclusion, the diurnal and sporadic variation of each testicular hormone is distinct, indicating that the major regulation is at the level of the hormone rather than at the endocrine cell type. Consequently, the balance of the hormones being released by the testes has complex variation during the day. The physiological significance of this will vary depending on which combinations of testicular hormones that the target cells respond to.