Technique for in Vivo Measurement of Thyroidal I131 in Cattle

Abstract

Equipment which makes possible the quantitative study of thyroidal I131 in the bovine is described. A scintillation counter mounted on a flexible arm, is attached to a head-holder designed to immobilize the head and neck of the animal. Sufficient sensitivity is provided by the counting system to permit the use of 50 or less uc of I131. Data on the normal uptake and release of I131 by the bovine thyroid and the effect of goitrogens upon reutilization of I131 from metabolized thyroid hormone are presented. One gram of thiouracil per 100 lb. inhibits reutilization. Replacement therapy with thyroxine during thiouracil treatment indicated the feasibility of measuring the daily secretion rate of individual animals in terms of L-thyroxine.