Obesity-related thyroiditis in childhood: relationship with insulin resistance

Background: Thyroid dysfunction is the most common hormonal abnormality in obesity. It should actually be considered as an adaptation response to fat excess. However, little has been reported on the morphology of the thyroid gland, and no data regarding the relationship between thyroid gland changes and metabolic parameters are available in obese adolescents. Objective: The study aimed to evaluate the frequency of non-autoimmune thyroiditis in obese adolescents and compare the metabolic status of patients with or without thyroiditis. Methods: A total of 218 obese children and 49 age-matched control healthy children were included. Thyroid ultrasonography (USG) was performed in all participants, as well as thyroid hormone levels, thyroid antibodies (Abs), lipid profile, homeostasis model assessment of insulin resistance (HOMA-IR) and high-sensitivity C-reactive protein (HsCRP) were determined. Obese children were divided into three groups according to the presence of thyroid autoantibodies and USG findings of thyroiditis (Group-1: Abs [-], normal thyroid morphology/Group-2: Abs [+], abnormal thyroid morphology/Group-3: Abs [-], abnormal thyroid morphology). The relationship between body mass index, metabolic parameters and thyroid gland status was analyzed. Results: Seventy-two of 218 obese patients (33%) had non-autoimmune thyroiditis (Group-3). The rate of insulin resistance was significantly higher in Group-3 than in Group-1 (p = 0.024). Similarly, the frequency of metabolic syndrome (MS) was higher in Group-3 (44.3%) than in Group-1 (27.1%) (p = 0.014). Conclusions: Obese adolescents with non-autoimmune thyroiditis had a higher incidence of insulin resistance. This finding supported the hypothesis that insulin resistance may have an effect on thyroid morphology. Further randomized trials investigating this relationship are required.