Thyroid regulatory function of intraocular pituitary transplants.

Abstract

Thyroid regulatory responses to thyroxine administration and to hemithyroidectomy have been studied in hypophysectomized rats bearing intraocular pituitary transplants. The intra-ocular graft, though separated from direct contact with the hypothalamus stimulated thyroid I131 uptake but did not influence other measures of thyroid function (I131 release rate, thyroid weight, PBJ). The grafts released ACTH but had no effect on growth or on testicular weight. In the presence of the graft but not in ungrafted hypophysectomized animals hemi-thyroidectomy was followed by increased TSH release as evidenced by a more rapid I131 release rate, stimulation of I131 uptake and thyroid enlargement. Thyroxine injection led to thyroid inhibition both in pituitary graft-bearing hypophysectomized and in normal animals, but not in ungrafted hypophysectomized rats. These findings were taken to indicate that pituitary tissue is capable of appropriate and autonomous TSH secretory responses to alterations in blood thyroid hormon...