Therefore, the present study has been undertaken to examine the local VD3 metabolism and the expression of VD3-related molecules (VDR, CYP27B1 and CYP24A1) in ovarian tissue and POAT of control rats (at proestrus and diestrus) and those with PCOS induced by the aromatase inhibitor letrozole. The gene discussed is CYP19A1; the disease is polycystic ovary syndrome.