THYROID FUNCTION STUDIES IN CHILDREN: NORMAL VALUES FOR THYROIDAL I131UPTAKE AND PBI131LEVELS UP TO THE AGE OF 18*

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Abstract
RADIOIODINE has been used in normal children to study thyroid function. All but one of the previous studies concerning children have been limited, in that only the concentrating ability of the thyroid for iodine has been tested. This function was measured as the percentage thyroidal uptake of the administered dose at twenty-four hours (1–6) or at forty-eight hours (7). In one study (8), the secretion rate of proteinbound radioiodine (PBI131) of serum was measured at various intervals after I131 administration, but there was no information about the age groups tested. This study was undertaken to establish normal standards for thyroidal uptake and serum PBI131 values at various ages and to clarify the discrepancies in normal uptake values reported from various parts of the United States. The data presented indicate that the thyroid gland in children up to the age of 4 years, and possibly later, is normally in a state of “hyperactivity” when compared to that of the euthyroid adult.