Alterations of thyroid function in overweight and obese children: An update

Background: Children with simple overweight and obesity may have alterations in the function of various endocrine organs. Abnormal function of the thyroid gland is seen in about one-fifth of children with obesity. The underlying mechanisms of obesity-associated thyroid dysfunction are still unclear, and hence, the specific treatment with levothyroxine (LT4) is controversial. This review discusses the causes of thyroid dysfunction and its management in pediatric obesity. Methods of Evidence Acquisition: The literature search for this narrative review was performed using international databases including PubMed/Medline, EMBASE, SCOPUS, and Google Scholar and relevant information was extracted from articles on thyroid dysfunction in obesity with an emphasis on the most recent studies. Results: The most common thyroid function abnormality in children with obesity is an isolated increase in thyroid-stimulating hormone (TSH) followed by minor changes in the ratios of triiodothyronine (T3) and thyroxine (T4). Several mechanisms have been proposed for the thyroid dysfunction in obesity, but none explains it fully, and hence, the clinical implications remain unclassified, and the specific treatment with levothyroxine is controversial. There are a few studies in children with obesity-related thyroid dysfunction and the effect of normalization of thyroid function on weight. However, there are limited data on the effect of normalization of thyroid function by either weight loss or levothyroxine (LT4) treatment on the various metabolic consequences closely associated with thyroid dysfunction in obesity. Conclusions: Further research is needed to elucidate the exact mechanisms of thyroid dysfunction in childhood obesity. In addition, larger studies are required to understand the beneficial effects of specific LT4 treatment on weight and on the other thyroid related metabolic derangements in childhood obesity, especially in view of the recent findings of induction of browning of white adipose tissue by thyroid hormones. Until new research establishes its benefits, specific LT4 treatment of thyroid dysfunction in childhood obesity should be avoided.