The serum levels of anti-Müllerian hormone (AMH) and vitamin D are positively associated in men and women, though not in boys, report Ian McLennan and colleagues. The study also reveals a seasonal variation of AMH levels in women that can be prevented by administration of vitamin D supplements in winter.

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AMH is produced exclusively by Sertoli cells in male individuals and by granulosa cells of the ovary in female individuals. This hormone has, therefore, become widely used as a marker of gonadal status. The functions and mechanisms of regulation of AMH are not fully understood. The previous identification of a vitamin D responsive element on the AMH gene promoter and the demonstration that vitamin D can upregulate transcription of AMH in vitro led McLennan and colleagues to investigate the potential relationship between AMH and vitamin D in humans.

The researchers measured AMH and 25-hydroxyvitamin D levels in the serum of 113 men aged 54–93 years, 33 premenopausal women aged 19–39 years and 74 boys aged 5–6 years from Dunedin, New Zealand. They observed a correlation between serum AMH and 25-hydroxyvitamin D levels in men and women, but not in boys (which they attribute to the very high expression of AMH in boys that could limit the effects of vitamin D). In the group of women, the levels of AMH were 18% lower on average in winter than in summer, a seasonal variation that was prevented by intake of a daily dose of 1,000 IU of vitamin D3 supplements in winter.

“Correlation studies cannot prove that a factor has an effect on another,” says Nathalie di Clemente from the University Paris-Sud, who was not involved in the study. She, nonetheless, agrees that the results indicate that AMH is regulated by vitamin D. “The authors should have a more homogeneous group of women to exclude the effects of ageing and ovarian disease,” she recommends.

“Vitamin D is the first environmental determinant of AMH levels identified,” says McLennan. “Adults with vitamin D deficiency will have lower levels of AMH, independent of their gonadal status,” he adds, “so the confounding effect of vitamin D deficiency should be considered when using AMH levels for clinical diagnosis.”