A Comparison of Triiodothyronine and Thyroxine in the Chick Goiter-Prevention Test

THE discovery of an unknown iodinated compound as a regular constituent of plasma and thyroid tissue (Gross et al., 1950) led to the discovery of triiodothyronine by Gross and Pitt-Rivers (1952). It has been established that triiodothyronine possesses all of the thyroid hormone qualities of thyroxine when tested in a variety of species (Gross and Pitt-Rivers, 1954). Moreover, triiodothyronine has proven to be from 3 to 7 times more potent than thyroxine in preventing thiouracil-induced thyroid goiter in rats (Gross and Pitt-Rivers, 1953; Tomich and Wollett, 1954). Since the above studies have been largely restricted to mammals, it seemed of some interest to determine the potency of triiodothyronine in terms of thyroxine in the fowl by means of the goiter prevention test. MATERIALS AND METHODS Experiments were performed on Single Comb White Leghorn cockerels maintained on commercial laboratory chow (containing 5 ppm. iodide) and caged under 24-hour infra-red illumination… .