ROLE OF THYROID-HORMONE IN CONTROLLING THE CONCENTRATION OF LUTEINIZING-HORMONE HUMAN CHORIONIC-GONADOTROPIN RECEPTORS IN RAT OVARIES

Little is known about the mechanism by which thyroid hormones influenc e ovarian function, especially in gonadotropin receptor formation. In this study the concentration of luteinizing hormone (LH)/human chorion ic gonadotropin (hCG) receptors in the ovaries of hypo- and hyperthyro id rats was estimated. Rats were made experimentally hypothyroid by th yroidectomy (N = 10) and hyperthyroid by injections of 40 mu g of L-th yroxine daily for 21 days (N = 14). After 3 weeks the ovaries were exc ised, weighed, immersed in liquid nitrogen and then, after 24 h of inc ubation with I-125-labeled hCG (CR-121), the concentration of receptor s (cpm) for one ovary and 1 mg of tissue was counted in their respecti ve homogenates. The ovaries of the hyperthyroid group were diminished in size and consequently the level of receptors per ovary also was red uced when compared with control animals. The number of receptors per o vary and per milligram of tissue of hypothyroid rats was three times h igher than in the control. In hyperthyroid animals a significant decre ase in these values was noted when compared with hypothyroid rats, esp ecially in the calculation of receptor concentration per ovary. It may be concluded that thyroid function may affect the size of the gland a nd also the number of LH/hCG-binding sites in rat ovaries. These data may be useful for interpretation of the pathophysiology of polycystic ovary syndrome In women and animals.