Circulating vitamin D correlates with serum antimüllerian hormone levels in women older than 40

AMH stands for AntiMullerian Hormone. It is also called MIS (Mullerian Inhibiting Substance).  Since AMH is produced directly by the ovarian follicles, AMH levels correlate with the number of residual eggs in the ovary.  It has been documented that women with lower AMH have lower antral follicular counts and produce a lower number of oocytes compared to women with higher levels.

In this study the authors  demostrated that 25OH-D was positively correlated with serum AMH levels in late-reproductive-aged (age ≥40 years) women.

The authors conclude:

There is some evidence suggesting that vitamin D deficiency might be involved in the pathogenesis of insulin resistance and the metabolic syndrome in polycystic ovarian syndrome (PCOS). In women with PCOS, low 25OH-D levels are associated with obesity and metabolic and endocrine disturbances  and vitamin D supplementation might improve menstrual frequency and metabolic disturbances in those women.   Because vitamin D induces the AMH gene  and because we found here that vitamin D and AMH are positively correlated, it is possible that vitamin D contributes to AMH actions by increasing AMH production by granulosa cells. These speculations warrant further investigation. ( Source : Fertility And Sterility)

At a minimum patients undergoing fertility treatments should be tested for vitamin D levels and Supplemented if  found deficient.