The aim of the study was to evaluate the natural course and potential risk factors of
autoimmune thyroiditis (AIT) and thyroid dysfunction, and their influences on growth and
glycemic control in children and adolescents with
type 1 diabetes mellitus (T1D). The study comprised 148 subjects (age range 1-21 years; males 51%) with T1D. During the interval of 12 years serum levels of
thyroid peroxidase (anti-TPO) and
thyroglobulin (
anti-TG) autoantibodies,
thyroid-stimulating hormone (TSH) and tyroksine (T4), were screened annually. Height,
weight, body mass index (BMI),
glycosylated hemoglobin (HbA1c),
insulin dose and the number of severe
hypoglycemic episodes, were recorded every 3 months. The mean follow-up was 7 +/- 4.1 years. Prevalence of AIT in subjects with T1D was 15.5%. It was significantly higher in girls (21.9% vs. 9.3%; p = 0.03). The mean age at AIT onset was 11.5 +/- 5.2 years. The mean interval between negative and positive AIT screening was 2.5 +/- 2.3 years. Cumulative incidence of AIT after 6 years of T1D duration was significantly higher in girls (30% vs. 15%; p = 0.03). Prevalence of
hypothyroidism was 8.1% with no significant differences in sex distribution. Prevalence of
hypothyroidism among subjects with elevated serum thyroid
antibodies was 52.2% with significant male preponderance (85.7% vs. 37.5%; p = 0.005). There were no subjects who developed
hypothyroidism in absence of thyroid
antibodies. Cumulative incidence of
hypothyroidism after 3 years from the moment of thyroid
antibodies appearance was 55% with significant male preponderance (85% vs. 40%; p = 0.005). The mean interval between T1D onset and
hypothyroidism development was 3.3 +/- 2.5 years, and between thyroid
antibodies appearance and hypothyreoidism development was 1.7 +/- 1.2 years. The mean age at
hypothyroidism onset was 12.7 +/- 5.3 years. There were no differences in growth and metabolic control between patients with and without AIT. The results of the present study confirmed frequent occurrence of AIT and thyroid dysfunction in subjects with T1D. The number of newly diagnosed subjects with AIT reached the peak at the age of puberty. Girls were significantly more predisposed to AIT at any age while amongst subjects with elevated thyroid
antibodies boys developed
hypothyroidism more frequently. Annual screening of thyroid
antibodies in all patients with T1D is recommended, while serum TSH level should be measured in patients with detected thyroid
antibodies.