Alterations in Thyroxine-I¹³¹ and Triiodothyronine-I¹³¹ Metabolism Produced by Thyroidectomy, Hypophysectomy and Adrenalectomy

¹ From the Department of Medicine, University of Washington School of Medicine, Seattle, Washington

The distribution of radioactivity was determined in certain tissues of normal, thyroidectomized, hypophysectomized and adrenalectomized rats, previously given I¹³¹-labeled thyroxine or triiodothyronine intravenously. It was found that blood levels of radioactivity were higher in thyroidectomized and hypophysectomized animals given labeled thyroxine than in control rats. Also, the sex difference in liver concentration of thyroxine radioactivity observed in the control animals was abolished by thyroidectomy or hypophysectomy, and the proportion of liver radioactivity which was soluble in trichloroacetic acid was elevated, with respect to controls, in the females alone. Also in the thyroxine groups, testicular radioactivity was lower in the hypophysectomized males than in control rats, but ovarian radioactivity was increased by hypophysectomy. Thyroidectomy and adrenalectomy resulted in higher levels of blood radioactivity following labeled triiodothyronine, but no other significant changes were observed.

Note:
with the technical assistance of Barbara Russell