The thyroid uptake of selenium-75-selenomethionine: effect of L-thyroxine and thyroid stimulating hormone.

The uptake of selenium-75-selenomethionine by the thyroid, parathyroid glands, and neck muscles has been estimated in rats using autoradiography ( 1). Selective labeling of the parathyroid glands was demonstrated in animals pretreated with thyroxine and low calcium diet. These qualitative observations led to the recommendation that triiodothyronine be administered to patients prior to parathyroid scanning on the premise that the regional uptake of this gammaemitting amino acid analogue would be greater in a hyperactive parathyroid gland than in surrounding suppressed thyroid tissue (2,3). Subsequent investi gations failed to demonstrate a thyroid hormone induced suppression of selenium75-selenomethionine uptake in the dog thyroid (4 ). In an effort to obtain a clearer understanding of the effect of thyroid hormones on the uptake of selenium-75selenomethionine by the thyroid, additional studies in rats and in humans, under going parathyroid surgery for hyperparathyroidism, were undertaken.