The cord serum thyroglobulin levels of 218 neonates are much higher than the levels after the first year of life and show a wide range. A relation exists between a shorter gestational age and increased thyroglobulin levels. The serum thyroglobulin levels decrease within a few months after birth, but throughout the first year of life, these levels are still higher than the normal values at later ages (5-35 ng/ml). IN 3 athyroid children, thyroglobulin is undetectable in serum.