Thyroxine-binding globulin cleavage in cord blood

Abstract

Thyroxine-binding globulin, a member of the serine protease inhibitor superfamily of proteins (serpins), releases T4 on cleavage by polymorphonuclear elastase. Such cleavage, previously shown to occur during sepsis and with an exogenous inflammatory stimulus, is now demonstrated in the cord blood of normal babies and appears to be part of a physiological inflammatory response in the newborn. In association with the neonatal TSH surge, thyroxine-binding globulin cleavage is likely to contribute to an increased flux of T4 to neonatal tissues at a time when T4-sensitive morphogenic and biochemical changes are occurring.