Resistance to thyroid hormone: clinical and biochemical paradox

This case report presents a male child in his middle childhood, diagnosed with resistance to thyroid hormone, a rare endocrine condition marked by diminished tissue responsiveness to thyroid hormones (THs) despite elevated circulating levels. The patient presented with neck swelling, nocturnal enuresis and tachycardia. Biochemically, he had elevated free T3 and T4 with inappropriately normal thyroid-stimulating hormone (TSH) levels. Clinical features reflected a mixed state of hyper- and hypothyroidism due to differential tissue distribution of thyroid hormone receptors (TRα and TRβ). Treatment included propranolol, amitriptyline, loperamide and vitamin D supplementation, resulting in symptomatic improvement. The case underscores the importance of considering thyroid hormone resistance beta (THRβ) in patients with discordant thyroid function tests and emphasises the role of genetic testing in establishing the diagnosis. It also highlights the phenotypic variability of THRβ and the need for individualised management. Differential diagnoses like TSH-producing adenoma (TSHoma), laboratory assay interference and drug-induced thyroid dysfunction were ruled out.