Observations concerning the binding of thyroid hormones in sera of normal subjects of varying ages.

Abstract

In man, from childhood through senescence, there occur alterations in several metabolic func- tions that are regulated in part by the thyroid hor- mones. Thus, aging is associated with a decrease in basal oxygen consumption per unit surface area and an increase in total serum cholesterol and beta-lipoprotein cholesterol (1-5). Several in- dexes of thyroid function per se indicate greater thyroid activity in children and adolescents than in young adults and, conversely, less thyroid ac- tivity in the elderly. The extensive literature on this subject has been considered in recent publica- tions (6, 7). It has been suggested, therefore, that there exist in childhood and senescence states of physiologic hyperand hypothyroidism, re- spectively (4, 6, 8). It is not clear, however, whether this is truly the case. In this regard it may be significant that, in contrast to the situation in clinically recognizable thyroid disease, the se- rum protein-bound iodine (PBI) varies little, if at all, throughout the life-span of man (6, 9, 10).