Evidence That Regulation of Thyrotropin Secretion by the Heterotopic Pituitary Is Independent of Endogenous Thyrotropin-Releasing Hormone from Any Source 1

Abstract

Abstract

Equal quantities of rabbit antithyrotropin-releasing hormone serum (TRH-AS) or normal rabbit serum (NRS) were administered to rats made hypothyroid by chronic feeding of propylthiouracil. TRH-AS produced a 37% decrease in plasma thyrotropin (TSH) (P < 0.01) in intact rats, but caused no significant decrease in plasma TSH concentration in hypophysectomized rats bearing three heterotopic pituitary transplants under the kidney capsule. NRS had no significant effect on plasma TSH in either group. This supports other data indicating that secretion of TSH and prolactin by heterotopic pituitaries is not under significant control by TRH in the general circulation.