Histological and biochemical changes in neonatal thyroid tissues.

The thyroid tissues of 17 infants who died between 3 hours and 46 days after birth were studied by histological and biochemical techniques. The morphological aspect and the iodine content of these tissues are not related to the gestational age of the neonates, but they are related to the survival time. There are dramatic events early after birth: desquamation of the epithelium and absence of colloid, low iodine content of tissue extract (less than 1 mu g 127I per mg of protein) and low percentage of thryoglobulin (less than 10%). 24 hours after birth, the vesicles fill with colloid and the epithelium is cuboidal; the iodine content of the protein increases (between 1 and 2 mu g 127I per mg protein) as well as the thyroglobulin percentate (around 20%). One week after birth, there is a maximum of colloid and flat epithelium; the iodine content of the protein extract is much higher (more than 2 mu g 127I per mg protein) as is thyroglobulin percentage (up to 40%). Our studies of thyroid tissues of neonates suggest that a leakage of colloid, iodine and thyroglobulin takes place in the perinatal period, this phenomenon being followed by their rapid repletion.