Obesity-related thyroiditis in childhood: relationship with insulin resistance

Abstract

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.

Is Waist-height Ratio Associated with Thyroid Antibody Levels in Children with Obesity?

“…We suggest that it is unnecessary to routinely investigate thyroid antibody levels in children with obesity, especially when thyroid function tests are within normal limits. In cases of seropositivity, a certain distinction of AITD may be challenging, given that thyroid changes in ultrasound is a common finding in cases with obesity ( 12 ). Further long-term follow-up studies investigating if weight loss reverses the abnormal findings in ultrasound and leads to a decrease in levels of thyroid autoantibodies would shed light on this topic.…”

“…Moderate elevation of thyrotropin (TSH) levels (subclinical hypothyroidism) is a common condition in children with overweight/obesity, with a prevalence ranging from 7% to 23%. However, prior studies offer conflicting results about thyroid hormone levels ( 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ). Nonetheless, it is accepted that TSH and thyroid hormone levels usually normalize with weight loss, from which it was interpreted that this is an adaptive response to lipid accumulation ( 2 , 3 , 4 ).…”

“…It was reported that obese cases with hyperthyrotropinemia and hypoechogenicity on thyroid ultrasound, but without thyroid autoantibody seropositivity, had normal cytological findings in ultrasound-guided fine needle aspiration biopsy specimens, which indicates the important role of thyroid antibodies in a diagnosis of AITD in obese patients ( 13 ). AITD was detected in only 19.5% of children with obesity and hyperthyrotropinemia and in 7.4% of children with normal TSH levels ( 3 , 12 ). Moreover, it has been shown that TPO-ab level was positively associated with BMI ( 7 ).…”

“…Although TSH and thyroid hormone levels in children and adults with obesity have been evaluated in numerous studies, the effect of obesity and lipid accumulation on thyroid autoantibody levels still remains unclear in children ( 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ). Obesity is well known to be a chronic inflammatory process ( 1 ).…”

“…In addition, increased leptin levels have been found to be associated with the presence of autoimmune thyroiditis disease (AITD) ( 10 ). However, results of studies of childhood obesity are slightly different, and non-autoimmune thyroiditis should be considered in the differential diagnosis before diagnosing AITD ( 3 , 12 , 13 ). It was reported that obese cases with hyperthyrotropinemia and hypoechogenicity on thyroid ultrasound, but without thyroid autoantibody seropositivity, had normal cytological findings in ultrasound-guided fine needle aspiration biopsy specimens, which indicates the important role of thyroid antibodies in a diagnosis of AITD in obese patients ( 13 ).…”