[Athyreotic congenital hypothyroidism in two sisters].

Two sisters with athyreotic congenital hypothyroidism are described. This is the fifth report on athyreotic congenital hypothyroidism in siblings. The elder sister is 14 years old and the younger one is 12. The parents have no consanguinity or family history of thyroid disease. Both of the patients were born before the start of neonatal screening tests for congenital hypothyroidism. After birth, they had jaundice, abdominal distention and constipation, which are typical symptoms of congenital hypothyroidism. Serum T4 levels were decreased, and the serum TSH levels were markedly increased. Therefore we diagnosed them as having congenital hypothyroidism. They have received replacement therapy with thyroxine since diagnosis and have shown normal development physically and psychologically. They were tested for thyroid scintigram when the elder sister was 9 years old and the younger one was 7. 123I thyroid uptakes were 0.69% and 0.64%, respectively. The thyroid scans demonstrated no focus of accumulation of 123I. They do not have trapping defect of iodine, because 123I ratio of saliva and serum were 41.3 and 46.3, respectively. From these results, we diagnosed them as having athyreotic congenital hypothyroidism. They and their mother do not have any antithyroid antibodies. We suppose that some genetic factor is responsible for the athyreotic congenital hypothyroidism.