Abstract:

The past decade has seen a renewed interest in ‘the sunshine vitamin’ vitamin D, because new evidence demonstrates benefits beyond bone health and an increase in the prevalence of vitamin D deficiency in the general population and in populations at risk, e.g. infants, adolescents, women of childbearing age and elderly. The well-established function of this steroid hormone is to maintain calcium and phosphorus homeostasis, and to promote bone mineralization. It has become the focus of many studies in recent years since vitamin D can have a significant influence on the growth and differentiation of a variety of tissues, and decreases the risk of many chronic illnesses including common cancers, autoimmune, infectious and cardiovascular diseases. The discovery that many tissues and cells in the body express a vitamin D receptor has provided new insights into the function of the vitamin. Reduced fertility rates and fertility capacity, diminished mating success, gonadal insufficiency, reduced aromatase gene expression, low aromatase activity, hypogonadism, uterine hypoplasia, impaired folliculogenesis and infertility have been described in vitamin-D-deficient animal models. Also, it has been reported that vitamin D affects placental steroidogenesis, expression of placental lactogen and decidualization of the endometrium. Confirmation of experimental human and animal observations establishing an association of vitamin D deficiency with adverse reproductive outcomes by high quality randomized clinical trials is still lacking. Therefore the objective of this chapter is to summarize the metabolism, epidemiology, and treatment of vitamin D deficiency but especially to focus on its role in reproductive health.