A double-blind, randomized, placebo-controlled trial, including 180 women with PCOS to receive vitamin D (20,000 IU/week) or placebo for 24 weeks [186], showed a decrease in plasma glucose one hour after the oral glucose tolerance test (OGTT) in the supplemented group although no significant effect on metabolic and endocrine parameters (menstrual frequency, testosterone, TC, TG, HbA1c, HOMA-IR, nor insulin sensitivity according to -QUICKI-) was found. The gene discussed is INS; the disease is polycystic ovary syndrome.