Suppression of luteinization in the baboon by thyrotrophin releasing hormone (TRH)

Parenteral administration of 40 μg of synthetic thyrotrophin releasing hormone (TRH) which began two days prior to ovulation and continued for four days suppressed the luteinization of corpus luteum as judged by the lower level of plasma progestin. In contrast, injections of saline had no effect. Simultaneous injections of 300 μg of synthetic LHRH in TRH treated baboons brought about a resumption of postovulatory rise of plasma progestin. Injections of TRH in the early luteal phase did not suppress the postovulatory rise of progestin. It is, therefore, inferred that injections of TRH suppress the midcycle LH rise and subsequently suppress the luteinization of corpus luteum, rather than exerting a direct effect on the ovary of the baboon.