The background of the study. Patients with type 1 diabetes mellitus have an increased risk of autoimmune thyroiditis, as defined by high serum antithyroid antibody concentrations or thyroid ultrasonography. In this study these tests were repeated in children and adolescents with type 1 diabetes three years after initial study.
How the study was done. In 1997, serum antithyroid peroxidase antibodies, thyrotropin, and thyroxine were measured, and thyroid ultrasonography was done in 105 children and adolescents with type 1 diabetes and 105 age- and sex-matched normal subjects. These tests were repeated in 2000 in 101 (96 percent) of the diabetic children and adolescents (47 girls, 54 boys; median age, 16 years; median duration of diabetes, 8 years).
The results of the study. Five of the 101 patients with diabetes (5 percent) had hypothyroidism initially; at follow-up three more patients had hypothyroidism. Four of these eight patients had a high serum antithyroid peroxidase antibody concentration, and all had attenuated echoes on thyroid ultrasonography. At base line, 13 patients (13 percent) had a high serum antithyroid peroxidase antibody concentration. At follow-up, 10 patients had higher concentrations and 3 patients had lower (but still high) concentrations. No patient who had a normal serum antithyroid peroxidase antibody concentration at base line had a high concentration at follow-up.
The median thyroid volume at base line was 9 ml in the patients and the normal subjects. At follow-up, it was 11 ml in the patients. Some ultrasonographic abnormality (usually decreased echoes) was present in 42 patients (42 percent) at base line and in 49 patients (48 percent) at follow-up; 33 (33 percent) had an abnormality at both times, 16 changed from normal to abnormal, and 9 changed from abnormal to normal. Ultrasonography was abnormal in 77 percent of patients with high serum antithyroid antibody concentrations and 44 percent of those with normal concentrations.
The conclusions of the study. The frequency of biochemical, serologic, and ultrasonographic abnormalities indicative of chronic autoimmune thyroiditis increases with time in children and adolescents with type 1 diabetes.
The original article. Hansen D, Bennedbaek FN, Hoier-Madsen M, Hegedus L, Jacobsen BB. A prospective study of thyroid function, morphology and autoimmunity in young patients with type 1 diabetes. Eur J Endocrinol 2003;148:245-51.