Vitamin D metabolism in polycystic ovary syndrome (PCOS)

Vitamin D is a steroid hormone, synthesized mainly by the skin on exposure to natural sunlight. Calcitriol, the active form of vitamin D, acts on target tissues binding to the nuclear vitamin D receptor. This receptor is expressed in different tissues, such as ovaries. In fact, in addition to its role in calcium-regulating tissues, vitamin D has been implicated in a wide range of extra-skeletal diseases including polycystic ovary syndrome (PCOS). A relatively high prevalence of vitamin D low levels is observed in women with PCOS (about 67%–85%). The exact role of vitamin D in the pathogenesis of PCOS remains unclear; however, several studies showed that the vitamin D pathway might be involved in the development of various symptoms of PCOS including ovulatory dysfunction with infertility, insulin resistance, hirsutism, and cardiovascular risk.