THYROID FUNCTION IN THE PREMATURE AND THE FULL TERM NEWBORN

Abstract

ABSTRACT Total and free serum thyroxine, plasma thyrotrophin (TSH) levels and, in some cases, the binding capacity of thyroxine-binding globulin (TBG) were measured in normal and premature newborns. In both groups, an acute release of TSH was observed in the first few hours of life, but this was prolonged over a period of 10 days in the premature newborns. The release of TSH induced, in both groups, an increase of total and free serum thyroxine (T4), reaching thyrotoxic levels. The TBG binding capacity, however, remains normal. This thyroid hyperactivity at birth reveals an important reserve of TSH in the perinatal period and the great metabolic needs of the foetus on the first day of life.