Study of antibody-dependent cell mediated cytotoxicity and thyroid growth blocking antibodies in congenital hypothyroidism

Antibody-dependent cell mediated cytotoxicity (ADCC) and thyroid growth immunoglobulin blocking (TGI block) which have been found in autoimmune thyroiditis in adults, as well as TSH receptors binding inhibitory antibodies (TBI ab) and antimicrosomal (Mc ab) and antithyroglobulin (Tg ab) antibodies were search in 42 mothers-infants pairs called at hospital after a positive screening for congenital hypothyroidism. The etiologic diagnoses were: 12 athyreosis, 12 ectopies, 7 anatomically normal glands and 11 transients. Tg ab and Mc ab were measured by commercial hemagglutination tests, TBI ab were determined using a radio ligand assay. ADCC in a 51Cr release assay by human thyroid cells in culture and TGI block by incorporation of 3H-thymidine using the same cells. Results were 38% for TBI ab in infants mainly in patients with dysgenesis without any concordance between mothers and infants. ADCC were found in 24% and TGI block in 24% with respectively mothers-infants concordance of 90% and 84%. Five mothers had autoimmune diseases (2 thyroiditis, 2 Graves' diseases and 1 insulin-dependent diabetes). Beside these rare cases of maternal diseases, the significantly high number of antibodies without any expression in the mothers suggests that autoimmunity plays a role in the etiology of congenital hypothyroidism.