Abstract
Summary
The effects of experimentally induced hypo-and hyperthyroidism on the ovarian response to pregnant mares' serum were determined in immature rats and mice by administering thiouracil for 4 to 20 days and thyroxine or thyroprotein for 10 days. A constant dose of PMS was injected into each animal during the last 4 days of each experiment and the increase in ovarian weight was measured. It was found in rats that all doses of thyroprotein or thyroxine significantly decreased the action of the gonado-trophin on the ovaries, while in mice thyroprotein significantly increased the ovarian response to PMS. When thiouracil was fed to rats for 4, 7, 10 and 15 day periods, there were significant increases in ovarian response to PMS, but when fed for 20 days thiouracil reduced the ovarian response to PMS. These data on young female rats and mice corroborate the results previously obtained in young male rats and mice. It is suggested that insofar as the ovarian response to PMS is concerned, young rats of both sexes secrete more and young mice less than an optimal amount of thyroid hormone.
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