Relationship of autoimmunity to thyroid dysfunction in children and adults with Down syndrome.

The extent to which autoimmunity contributes to thyroid dysfunction in Down Syndrome (DS) individuals has not been clarified. We studied 61 persons (34 males and 27 females) with DS (age 5 months to 48 years) for the presence of thyroid autoantibodies (thyroid microsomal antibodies and thyroglobulin antibodies), pancreatic islet cell autoantibodies, gastric parietal cell autoantibodies, and adrenocortical autoantibodies. Thyroid function was determined by measurement of TSH. HLA-A, B and -DR typing was performed on 52 subjects. Forty of 61 subjects (66%) had thyroid dysfunction: elevated TSH values (greater than 5 mcIU/ml) were found in 35 of 61 individuals; 3 subjects had previously documented Hashimoto thyroiditis and were on therapy for hyperthyroidism; and 2 persons had Graves disease. No age or sex variation was detected. Seventeen (28%) subjects had thyroid autoantibodies. Fifteen of the 17 had thyroid dysfunction. Twelve of 25 subjects (48%) over 10 years with thyroid dysfunction had thyroid autoantibodies compared to only 3 of 15 (20%) under the age of 10 years. However, children less than of 10 years tended to have higher TSH values. Only 1 individual who had thyroid antibodies had gastric parietal cell autoantibodies present. Islet cell and adrenocortical autoantibodies were not found in any individuals. Neither thyroid dysfunction nor thyroid autoantibodies correlated with any HLA allele. These findings suggest that thyroid dysfunction in individuals with DS of all ages is a common heterogeneous disorder which cannot be solely explained on the basis of autoimmunity. We recommend that thyroid function be followed closely whether or not thyroid autoantibodies are present.