NEONATAL HYPOTHYROXINEMIA - EFFECTS OF IODINE INTAKE AND PREMATURE BIRTH

We have investigated the effects of iodine (I) intake on urinary I exc retion in preterm (PT) babies up to 2 months after birth and its effec t on serum T-4, free T-4 (FT4), T-3, TSH, and thyroglobulin (Tg) level s compared to those in term (T) newborns. Very premature and very sick infants were in negative I balance for the first weeks after birth. L ater, these same infants, as well as the other PT and T newborns, were in positive balance; 75-80% of the ingested I was not accounted for i n the urine. The urinary I levels of PT and T neonates cannot be equat ed to their I intakes. T-4, FT4, and T-3 levels in PT and T neonates i ncreased with postmenstrual age, whereas Tg decreased and TSH did not change. Serum FT4, T-3, Tg, and TSH levels in PT neonates were affecte d negatively, independently from age, by a low I intake. PT birth also affected T-4, FT4, and Tg negatively, independently from I intake and postmenstrual age, for at least 6-8 weeks after birth. Care should be taken to avoid I deficiency in PT neonates. However, even when I inta ke is adequate, PT newborns are hypothyroxinemic compared to T babies during an important period of brain development. This suggests the pos sible convenience of interventions that might mimic the intrauterine h ormone environment and accelerate maturation.