Hyperinsulinemia and human chorionic gonadotropin synergistically promote the growth of ovarian follicular cysts in rats.

Tonically elevated serum luteinizing hormone (LH) and hyperinsulinemia are prominent features of polycystic ovary syndrome (PCO) in women, but the relative roles of LH and insulin in the pathogenesis of PCO is still unknown. The present study was undertaken to determine the effect(s) hyperinsulinemia might have on the induction of follicular cysts by LH/human chorionic gonadotropin (hCG) in the rat. Beginning on day 85 of age, adult female rats were given one of the following in vivo treatments: (1) vehicle alone; (2) a high-fat diet to control for the effects of weight-gain; (3) up to 6 U insulin per day; (4) 50 micrograms gonadotropin-releasing hormone (GnRH) antagonist (GnRHant) per day; (5) 1.5 IU hCG twice daily; (6) insulin + hCG; (7) insulin + GnRHant; (8) hCG + GnRHant; or (9) hCG + insulin + GnRHant. After 22 days of treatment, animals were killed on day 23, trunk blood was collected, and ovaries were excised for histological study. Regular cycles, assessed by vaginal smears, ceased after 10 days for most animals in treatment groups receiving hCG, but continued in all other treatment groups. All the animals in each hCG-treated group developed either unilateral or bilateral cystic ovaries, while no animals in the groups not receiving hCG developed follicular cysts. More animals from each group treated with both hCG and insulin possessed bilateral ovarian cysts than did rats treated with hCG alone: 80% and 60%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)