Male rats bearing multiple heterotopic pituitaries under the renal capsule were hypophysectomized. Two weeks later the effects of propylthiouracil feeding on thyroid size and of forebrain removal on thyroid radioiodine metabolism were studied. Two weeks of propylthiouracil feeding failed to induce goiter formation in hypophysectomized rats with 2 to 16 pituitaries. In hypophysectomized rats with 10 heterotopic pituitaries, complete forebrain removal, but not cerebral decortication, reduced the 4-h thyroidal uptake of 131I and formation of 131I-labeled iodothyronines one day following brain operations. This finding suggests that the subcortical forebrain maintains the TSH secretion of heterotopic pituitaries. Presumably TRF is secreted by the subcortical forebrain and passes through the general circulation to stimulate TSH secretion of heterotopic pituitaries. Apparently the level of TRF reaching heterotopic pituitaries through the general circulation never can attain the levels reached in the hypophyseal portal system.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Endocrine and Autonomic Systems
- Cellular and Molecular Neuroscience