INFLUENCE OF THE THYROID GLAND ON PITUITARY GONADOTROPHIC ACTIVITY IN THE RABBIT121,2

Abstract

In thyroidectomised rabbits, the ovaries contain many more large follicles than in normal controls. However, ovulation does not take place after coitus or after the inj. of Cu acetate. The operated animals readily ovulate after the inj. of pregnancy urine extract and the ruptured follicles are more numerous than in normal estrous animals. Fresh hypophysial saline extracts were prepared from the normal and thyroidectomised rabbits for the assay of their relative amts. of ovulating hormone The extract from the normal animals caused 60% ovulation in the estrous rabbits, whereas extract from thyroidectomised rabbits caused no ovulation but induced the growth of follicles. Furthermore, thyroidectomised [female][female] were very sensitive in ovulation reaction to the inj. of normal hypophysial extract, but they failed to ovulate when injected with similarly prepared extract from thyroidectomised animals. The hypophysis of thyroidectomised rabbits is apparently of ovulating hormone, whereas the follicle stimulating hormone may be considerably increased.