Considerable information has accumulated regarding newborn metabolic functions including data suggesting interesting alterations in several parameters of thyroid function during the neonatal period. During the first several days of life, beginning as early as 12 to 24 hours of age, serum hormonal iodine values reach hyperthyroid levels.1-3 There is a subsequent fall to normal levels by 2 to 3 weeks. Dowling et al.4 have shown that thyroxine-binding capacity in the sera of infants, though increased, is less than that of their mothers. Spafford et al.5 and Marks et al.6 have demonstrated a relative increase in I131-labeled triiodothyronine red blood cell uptake in infants during the first week indicating that the neonatal elevation of serum hormonal iodine is not due to the increased thyroxine-binding protein. Neither can it be accounted for by dehydration. The extrathyroidal hormonal iodine pool must actually be increased during the
FISHER DA, ODDIE TH, BURROUGHS JC. Thyroidal Radioiodine Uptake Rate Measurement in Infants. Am J Dis Child. 1962;103(6):738–749. doi:10.1001/archpedi.1962.02080020755002
Pediatrics in JAMA: Read the Latest
Customize your JAMA Network experience by selecting one or more topics from the list below.