LAUSR

Introduction Vitamin D is involved in the regulatory mechanisms of ovarian function and is frequently low in PCOS patients. Since obesity and hyperinsulinemic state negatively influenced vitamin D levels, therefore, we evaluated the production of vitamin D at the ovarian level only in lean and normoinsulinemic PCOS subjects. Basal, GnRH analogue-induced ovarian production of 25OH-vitamin D (VitD) and a direct sampling at ovarian vein level were investigated. Methods Basal and GnRH analogue-induced hormone levels were evaluated at peripheral level in 45 subjects, aged 18–39 years, and in 22 healthy women with age- and BMI-matched as controls. In 12 PCOS patients, undergoing laparoscopy, a venous sampling at both peripheral and ovarian level was further done. All subjects presented low VitD levels, appropriate to the season and with no difference between PCOS and control subjects. Results GnRH analogue significantly stimulated plasma LH, FSH, 17-OHP and estradiol secretion ( p from < 0.05 to < 0.001 vs basal levels), whereas no effect was observed on both serum AMH and VitD concentrations in all groups. A significant difference ( p  < 0.006), between peripheral and ovarian veins , was observed in both AMH and estradiol levels in PCOS subjects, while no gradient of VitD was detected. Conclusions All patients presented with low VitD levels. The absence of any VitD variation, both at basal and after GnRH analogue administration, or at peripheral-ovarian vein gradient, suggests no pituitary–ovarian axis involvement in VitD production or its direct ovarian production in lean and normoinsulinemic PCOS subjects.