Thyroid function, morphology and autoimmunity in young patients with insulin-dependent diabetes mellitus

Objective: An association between insulin-dependent diabetes mellitus (IDDM ) and autoimmune thyroid disease is well recognized, We have studied the pr evalence of thyroid dysfunction, autoimmunity and morphological abnormaliti es by ultrasonography in young diabetics. Subjects and methods: Among young IDDM patients less than 18 years old and living in the county of Funen, De nmark, 105 of 116 eligible patients participated. They were compared with 1 05 healthy children matched for sex and age. Routine thyroid function param eters (thyroxine (T-4), tri-iodothyronine (T-3). T-3 resin uptake and TSH) and thyroid autoantibodies (anti-thyroid peroxidase, TPOab, and thyroglobul in antibodies, Tgab) were measured. Thyroid size and morphology were determ ined by ultrasonography. Results: Two of the diabetics had previously diagnosed hypothyroidism and t hree new cases of subclinical hypothyroidism were found, There were no sign ificant differences in thyroid function variables or thyroid volume between diabetics and controls. Thyroid volume correlated significantly with age a nd weight in both groups. Among diabetics, 17 had thyroid autoantibodies (1 3 with TPOab, 14 with Tgab and 10 with both) compared with 2 children in th e control group (P<0.001). Forty-four with IDDM as opposed to 11 of the con trols (P<0.001) had morphological abnormalities at ultrasonography, Most of them had various degrees of hypoechogenicity thought to be a marker of thy roid autoimmunity Among the 17 diabetics with autoantibodies, 10 had morpho logical abnormalities at ultrasonography. Conclusions: A high proportion of young IDDM patients without any clinical signs of thyroid disease have markers of thyroid autoimmunity. Many have th yroid autoantibodies, but even more have abnormalities by thyroid ultrasono graphy.