Detection of circulating autoantibodies against thyroid hormones in an infant with permanent congenital hypothyroidism and her twin with transient congenital hypothyroidism: possible contribution of thyroid hormone autoantibodies to neonatal and infant hypothyroidism.

Premature, very-low-birth-weight female twins were diagnosed with congenital hypothyroidism (CH). Thyroid hormone antibodies (THAb) directed against triiodothyronine (T3) and thyroxine (T4) of both the IgM and IgG class were detected in both twins. At age 10 months, a rise in thyroid stimulating hormone (TSH) occurred in both infants and measurement of THAb at the same time revealed the appearance of IgM-T4 and IgG-T4 and an increase in IgG-T3 levels in twin 1 (permanent CH), and with a slight increase of IgM-T4 and IgG-T4 levels and appearance of IgM-T3 in twin 2 (transient CH). THAb may contribute to the induction of hypothyroidism in neonates and infants, especially those with underlying autoimmune thyroid disease.