VDR and polycystic ovary syndrome: Herein, we investigated differences in the expression of VD3 receptor (VDR) and key VD3 metabolic enzymes, 1α-hydroxylase (CYP27B1) and 24-hydroxylase (CYP24A1), in the ovary and periovarian adipose tissue (POAT) of control (proestrus and diestrus) and PCOS induced by letrozole rats.