It is usually necessary to diagnose congenital hypothyroidism promptly after birth if administration of thyroid hormone is to be started in time to produce reasonable intelligence.1,2 The normal values for laboratory tests of infants' thyroid function, as determined by presently accepted methods, have recently been summarized by Pickering et al.3 The serum protein-bound iodine concentration (PBI), butanol extractable iodine concentration (BEI), and the thyroid I131 uptake test are included in this summary. These tests have certain disadvantages in the newborn in that the PBI, BEI, and I131 uptake are all markedly altered by administration of inorganic or organic iodine to the patient. Furthermore, the thyroid I131 uptake test exposes the thyroid gland of the infant to radiation.
Therefore, we have studied the thyroid status of a series of normal infants by the in vitro I131l-triiodothyronine (TRI) red blood cell uptake test of Hamolsky et
SPAFFORD NR, CARR EA, LOWREY GH, BEIERWALTES WH. I131 Labeled Triiodothyronine Erythrocyte Uptake of Mothers and Newborn Infants. Am J Dis Child. 1960;100(6):844–849. doi:10.1001/archpedi.1960.04020040846006