High leptin levels may lead to IR in nonobese PCOS patients by promoting the following events: (i) inhibition of phosphoenolpyruvate carboxykinase, causing decreased hepatic glucose oxidation and increased hepatic glycogen reserve; (ii) fat deposition in skeletal muscle cells; (iii) fat breakdown and free fatty acid production; and (iv) direct inhibition of basal insulin secretion and glucose-stimulated insulin secretion. This evidence concerns the gene INS and polycystic ovary syndrome.