The Protein-Bound Iodine in the Fowl

IT HAS been established that measurement of the serum or plasma protein-bound iodine (PBI) is a dependable index of circulating thyroid hormone and, therefore, an index of thyroid activity in mammals (Blau, 1933; Leland, 1932; Taurog and Chaikoff, 1947; Laidlaw, 1949; and Leblond and Gross, 1949). The situation in birds, however, has remained uncertain. It has been reported (Mellen and Hardy, 1957) that experimental alteration of thyroid activity did not produce changes in the blood PBI level in chickens as determined by a chemical method. Bumgardner and Shaffner (1957) reported that the chemical method of PBI determination which they employed was not sensitive enough to measure differences in the thyroid activity of the chick. Lachiver and Poivilliers-de la Queriere (1959) used radioactive iodine to investigate the PBI in pigeons which had been radiothyroidectomized. These workers reported that the PBI131 values were useful. While the current investigations were being conducted,…