A STUDY OF THE UPTAKE OF IODINE (I-131) BY THE THYROID OF PREMATURE INFANTS
In a series of 65 premature infants weighing from 991 to 2481 gm. and 5 full-term infants from 2522 to 2694 gm., who were from 1 to 63 days old, the uptake of I-131 by the thyroid 24 hours following the administration of 5 µc. orally or by means of a polyethylene tube in the stomach, as measured by both a Geiger-Mueller counter and a scintillation counter, ranged from 10 to 60 per cent. In 2 cases with an uptake of less than 10 per cent and 3 cases bordering 60 per cent, technicalities and the possible surreptitious use of thyroid by the mother may account for the variation. The range of uptake of I-131 as recorded in this series of infants is within the limits of normal as recorded in studies of children and adults using the Geiger-Mueller counter. The difference in percentage uptake as recorded by the Geiger-Mueller counter and the scintillation counter, after acquiring experience with the equipment, was less than 5 per cent. The technique, and the scintillation counter used, are described. I-131 administered orally or by a polyethylene tube in the stomach is well tolerated and in this series did not cause vomiting. The activity of the thyroid gland in premature and full-term infants, as revealed by the uptake of I-131 24 hours following administration, is discussed and evidence is presented that in such individuals the thyroid functions in a manner similar to that found in children and adults.