Blood protein-bound iodine in the fowl.

Abstract

EARLY studies of serum or plasma protein-bound iodine (PBI) showed it to be a reliable and valuable criterion of thyroid state in humans (1, 2). Subsequent studies have largely confirmed this observation, and, in the opinion of some clinicians, PBI “is probably the single most reliable test of thyroid function” (3). In recent years, workers interested in the physiology of domestic mammals have studied blood PBI in relation to other characteristics of physiological and economic importance. Long et al. (4) found significant breed differences in PBI of dairy cattle, and also noted that calves had higher PBI levels than cows. Burns et al. (5) reported a highly significant correlation between PBI and metabolic rate in bulls. In beef calves, there is apparently an optimum PBI level associated with the best rates of gain (6), while in Hampshire swine, a significant negative correlation between PBI level and average daily gain has been reported (7). In a study of adrenal cortex-thyroid relationships in ketotic co...