In children, abnormal thyroid function tests (TFTs) can present diagnostic difficulty due to the variety of clinical manifestations that may accompany them. Pediatric patients with abnormal TFTs are discussed in this article, along with their differential diagnoses and approaches to management. The most prevalent causes of pediatric hypothyroidism and hyperthyroidism, including Hashimoto’s thyroiditis and Graves’ disease, are thoroughly reviewed. Additionally, we explore other potential etiologies of abnormal TFTs in children: congenital hypothyroidism, resistance to thyroid hormone, nonthyroidal illness syndrome, medication use, iodine deficiency, and interferences with thyroid function immunoassays. In the setting of the pediatric population, diagnostic assessment and analysis of TFTs involving thyroid-stimulating hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3) are addressed.

Keywords: Free thyroxine, free triiodothyronine, hyperthyroidism, hypothyroidism, pediatric, thyroid-stimulating hormone, thyroid function tests