[The functional interrelationship of the ovaries and the thyroid]

The character of the estrous cycle was studied in mature rats with different variants of the experimental hypophyseal-thyroid imbalance. This state was caused by injecting rifathyroine--a synthetic analogue of thyroliberin, thyrotropin and L-thyroxin to rats having a stable 4-days estrous cycle. The above manipulations were made either in the morning hours of proestrus when a rapid growth of dominant follicles takes place in the ovary, or at the stage of diestrus when new ovarian follicles start growing. The effect of injecting rifathyroin nonspecifically stimulating the release of prolactin by the adenohypophysis was dependent on the stage of the estrous cycle in which the animal was when injecting the drug was started. If it was the proestrus, the duration and sequence of the estrous cycle phases was not changed. If injecting rifathyroin was started at diestrus, in 6 of 11 animals this stage was as long as the whole cycle period. An experimental elevation of the content of thyrotropin caused by a single injection resulted in a disturbance of the duration and sequence of phases of the estrous cycle in all the animals. If thyrotropin was injected within the first hours of proestrus, this phase became shorter and the ovulation did not take place. An injection of thyrotropin during diestrus prolonged the latter for the whole period of observations equal to the cycle duration. Injections of L-thyroxin failed to change the sequence and duration of the cycle phases practically in half of the experimental animals, independent of the phase when the injecting was started. In 6 of 11 rats given the first injection of L-thyroxin at the stage of proestrus the anestrus and a prolonged phase of diestrus (during the whole cycle) were observed afterwards.(ABSTRACT TRUNCATED AT 250 WORDS)