The unexpected finding of insulin-induced improvement in ovulatory menstrual cycle function in PCOS-like female monkeys may reflect the well-documented action of insulin as a co-gonadotropin [22,41,83,92], possibly acting through insulin receptors on ovarian follicle cumulus and mural granulosa cells [82], as well as theca cells [41]. Here, INSR is linked to polycystic ovary syndrome.