Thyroid activity in adult and neonate Harp seals Pagophilus groenlandicus



Serum thyroxine (T4) and triiodothyronine (T3) levels were higher in neonate seals compared with adults. The appearance of the thyroid gland in neonates was markedly variable but in both neonate and adult Harp seals the thyroid appeared relatively inactive except in one of the specimens examined. The data suggest that the different hormone levels in adult and neonate represent the respective euthroid state for Harp seals at these stages in their life.