It is well documented that thyroid hormones (THs) are involved in energy and lipid metabolism, thermogenesis, and body weight control, acting on several tissues. Thus, any change in thyroid status may affect body weight and metabolic rate. On the other hand, fibroblast growth factor 21 (FGF-21) is a complex hormone involved in energy, lipid, and glucose metabolism, sharing common biochemical pathways and sites of action with THs. FGF-21 is synthesized and acts primarily on the liver, but weaker expression has also been described in muscle, pancreas, and adipose tissue. In addition, FGF-21 acts through endocrine and paracrine mechanisms, regulating metabolic pathways such as fatty acid oxidation, glucose uptake, and thermogenesis. Recent animal and human studies have highlighted a close bidirectional relationship between FGF-21 and THs, partially elucidated. Thyroid hormones regulate the expression of the FGF-21 gene in the liver and can also increase FGF-21 levels in vivo. However, it has also been suggested that some of their key actions are largely independent. Data on FGF-21 levels and their metabolic role in pediatric patients with chronic autoimmune thyroiditis (AIT) are scarce. This study aims to measure FGF-21 serum levels in children and adolescents with Hashimoto's thyroiditis and investigate any possible associations between FGF-21 serum levels and resting metabolic rate (RMR) and levothyroxine (LT4) treatment, or other clinical and biochemical parameters.
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Fibroblast Growth Factor 21 (FGF-21)
Timeframe: baseline and 6 months
RMR/Weight/Day
Timeframe: baseline and 6 months