Vitamin D is one of the steroid hormones. The precursor of vitamin D, 7-dehydrocholesterol, which is an intermediary for cholesterol pathway, is available in the skin. Ultraviolet B (UVB) radiation makes the transformation of 7-dehydrocholesterol to provitamin D3, which automatically isomerizes to cholecalciferol (vitamin D3). Vitamin D3 is secreted into blood circulation and carried by the vitamin D–binding protein (VDBP). Around 80–90% of vitamin D is from sunlight-derived production in the skin. A little amount of vitamin D is also extracted from foods and/or additional supplementation. Vitamin D has been well known for its function in maintaining calcium and phosphorus homeostasis and promoting bone mineralization. Accumulating evidence from animal and human studies suggests that vitamin D also modulates reproductive processes in women and men and is involved in many functions of the reproductive system. Vitamin D receptor (VDR) and vitamin D–metabolizing enzymes are found in reproductive tissues of women and men. This chapter presents an up-to-date review for describing the function of vitamin D in female reproduction throughout reproductive ages from menarche to menopause, during pregnancy and lactation, and some disorders affecting women and also the role of vitamin D applied to male fertility.
Part of the book: A Critical Evaluation of Vitamin D