Type 1 Diabetes and Thyroid Autoimmunity in Children

Autoimmune thyroid disease and type 1 diabetes (T1DM) are two autoimmune diseases frequently associated, especially in pediatric population. Aims: we wanted to determine and ilustrate the relationship between type 1 diabetes and autoimmune thyroiditis and also the factors than can influence it, like gender, age, diabetes duration. Glycemic control was also evaluated for all the patients.

There were studied 256 patients, children and adolescents with T1DM (male/ female: 145/115; 55%/45%). Anti-TPO antibodies were detected using the electrohemiluminescence method and glycosylated haemoglobin A1c (HbA1c) was measured through a imunoturbidimetric method. The patients were clinically examined, including thyroid gland palpation, blood pressure measurement and assessment of their pubertal status and growth.

Age distribution at the time of T1DM diagnosis: most of them, 26% were diagnosed between 6 and 9 years, 23% between 1-3 years, 21% between 3-6 years, 19% between 9-12 years, 9% between 12-15 years, and very few of them (2%) were diagnosed between 15 and 18 years. Among these patients, 47/256 (18.3 %) were positive for thyroid antibodies (anti - TPO). In 2 of 47 patients tests for anti TPO antibodies were positive at the time of T1DM diagnosis. Tests for anti - TPO antibodies became positive with an average of 5.09±3.84 ( range 0-13) years after the diagnosis of T1DM. At the time that anti - thyroid antibodies were first seen to be positive all patients were euthyroid with a mean age of 11.3 years (range 4 -16) and a mean diabetes duration of 5.21±3.57 (range 0-9 years). After 5±3.3 years (range 0- 9 years) a progression towards subclinical hypothyroidism due to Hashimoto thyroiditis was observed in 41 from 47 patients (87.2%), while no patient developed clinical hypoythyroidism. It was observed an 9.2 % ±1.5% mean value of HbA1c in patients with thyroiditis comparative with 7.9 % ± 0.7 % mean HbA1c value in those without thyroiditis.

Thyroid autoimmunity is frequently present among T1DM patients, can be associated with increased age, female gender, long diabetes duration, and can inbalance the glycemic control of T1DM patients.