State of ovarian function in experimental hyperthyroidism and hyperthyrotropinemia

Abstract

The effect of experimental hyperthyroidism and hyperthyrotropinemia on histophysiological processes in the female reproductive system is studied. Thyroid hormones and thyrotropin are found to exhibit a pronounced modulatory effect on morphogenetic processes in the female gonad. Key Words: ovary; thyroid gland; folliculogenesisNumerous aspects of regulation of the morphogenetic basis of ovarian function have been studied at length. However, there is now a need to broaden the known basic regulating system (hypothalamuspituitary-gonads) by adding the complex of extraand intraorgan modulators. The specific regulators of cyclic ovarian function, the gonadotropic hormones, are complexes of hormone-regulated isoforms, the specificity of which is determined by the endocrine status of the organism. Recent investigations point to a close relationship between dysfunctions of the female reproductive and thyroid systems. The morphophysiological basis of this relationship remains to be explored. The aim of the present study was to investigate the state of the female gonad under conditions of experimentally induced hyperthyroidism and hyperthyrotropinemia. MATERIALS AND METHODSThe ovaries of mature random-bred rats with a stable 4-day estrous cycle were studied. The animals of group 1 were repeatedly injected with triiodothyronine (T3) in a single dose of 0.3 g/kg. In group 2 hyperthyrotropinemia was modeled by injecting Department of Histology and Embryology, Pediatric Faculty, Russian State Medical University, Moscow thyrotropic hormone (TSH) in single doses of 0.05 IU. The above interventions were started in some animals from proestrus and in others from the first day of diestrus. The characteristics of a single cycle were analyzed. The control animals were injected with the same volume of vehicle.In some animals ovulation was artificially stimulated to elucidate the mechanisms of ovarian dysfunction. Changes in the cycle were judged from vaginal smears. Serial histological slices were studied using a routine histological method as well as the method of differential follicle count (according to a published classification [2]). The hormone content in the peripheral blood was determined by radioimmunoassay. RESULTSOut of 33 rats injected with T 3 starting from proestms the cycle remained unchanged in 15 and permanent diestms (anovulation) was established in 18 animals. Out of 15 rats injected with T 3 starting from diestms the onset of permanent diestrus occurred in 10 and the physiological cycle was preserved in 5 rats. On day 4 of permanent diestrus the histological structure of the ovaries was analyzed and folIlIl~cles of various stages were counted. Radioimmunoassay of the T 3 content in the blood