Thyroid function and thyroid autoimmunity in patients with type 1 diabetes mellitus.

OBJECTIVE An association between diabetes mellitus and autoimmune thyroid disease is well known. We have investigated the prevalence of thyroid dysfunction and autoimmunity in type 1 diabetic patients. METHODS Seventy-nine type 1 diabetic patients were recruited in the study, and underwent complete investigations for thyroid function, which included free thyroxine, free tri-iodothyronine, and thyroid stimulating hormone, of those only 64 patients had performed thyroid autoantibodies (TAb); anti- thyroid peroxidase antibodies (TPOAb) or antimicrosomal antibodies and thyroglobulin antibodies (TgAb). They were compared with 127 healthy subjects matched for sex and age. This study was carried out at the National Center for Diabetes, Endocrinology and Genetics, Jordan University, Amman, Jordan between 2000 and 2001. RESULTS In the diabetic group, 7 cases (8.9%) of thyroid dysfunction were detected, 4 of these were diagnosed as subclinical hypothyroidism, whereas the other 3 had overt hypothyroidism and were on thyroxine replacement therapy. In the control group, 6 (4.7%) subjects were diagnosed as subclinical hyperthyroidism. There was a significant difference in thyroid function variables between diabetics and controls. Among type 1 diabetic patients, 7 (9.2%) had thyroid autoantibodies, 5 with positive TPOAb only and 2 with positive TAb; TPOAb or antimicrosomal antibodies and TgAb; compared with 8 (6.3%) in the control group, 4 with positive TPOAb only and 4 with positive TAb; TPOAb or antimicrosomal antibodies and TgAb P=0.68. CONCLUSION Biochemical thyroid dysfunction and thyroid autoimmunity were evident in type 1 diabetics who were apparently euthyroid, with no significant difference between diabetics and controls.