Histological structure of the thyroid gland in the newborn. With special reference to hypotrophy, hydrops fetalis and Cesarean section delivery.

Histological features of the thyroid gland in the newborns have been described under several circumstances; gestational age, length of survival, and under particular clinical status such as hypotrophy (intrauterine growth retardation), Cesarean section delivery and hydrops fetalis. Gestational age does not modify significantly the histological aspect of the thyroid, while birth process and adjustment to extrauterine life induce dramatic changes such as severe depletion of colloid for about 24 h, followed by a massive repletion after the first day of life. A few exceptions to this phenomenon are described. Thyroid glands of hypotrophic infants and of infants delivered by cesarean section exhibit colloid-filled vesicles already within the first day. Thyroid glands of hydrops fetalis have a reverse tendency. This phenomenon might be secondary to multiple exchange transfusions.