Endocrine Abstracts

Accumulating evidence from animal and human studies suggests that vitamin D is involved in many functions of the reproductive system in both genders. In women, vitamin D status has been associated with in vitro fertilization (IVF) outcome, features of polycystic ovarian syndrome (PCOS), endometriosis, and sex hormone steroidogenesis. In detail, cross-sectional data suggest a regulatory role of vitamin D in PCOS-related aspects such as ovulatory dysfunction, insulin resistance as well as hyperandrogenism. Moreover, results from randomized controlled trials (RCTs) suggest that vitamin D supplementation may be beneficial for follicular development and menstrual cycle regulation in PCOS women. Although several data converge towards a beneficial effect of vitamin D supplementation in metabolic disturbances in women with PCOS, this remains to be demonstrated in high-quality RCTs. Regarding assisted reproductive techniques, recent studies suggest that vitamin D supplementation might be beneficial for couples undergoing IVF. In men, vitamin D status has been associated with semen quality and sperm count, motility and morphology as well as with androgen levels in both fertile and infertile men. Further, there is evidence for a favourable effect of vitamin D supplementation on semen quality, fertility outcomes as well as on testosterone concentrations. In summary, vitamin D deficiency may be a risk factor for adverse fertility outcomes, there is, however, insufficient evidence to establish causality. High quality RCTs are needed to further evaluate the effects of vitamin D supplementation on fertility and sex hormone steroidogenesis in women as well as in men.