Subacute thyroiditis presenting with thyrotoxicosis and a non-suppressed TSH: a two-case report

Open Access

Abstract

Subacute thyroiditis (SAT), or de Quervain thyroiditis, is a self-limiting inflammatory disorder of the thyroid that typically presents with anterior neck pain, thyroid tenderness, systemic inflammatory features, and transient thyrotoxicosis. The thyrotoxic phase usually results from destructive release of preformed thyroid hormones rather than increased thyroid hormone synthesis. A suppressed serum thyroid-stimulating hormone (TSH) concentration is therefore expected in most patients during the thyrotoxic phase.We report two patients with clinically typical painful subacute thyroiditis who presented with biochemical elevation of free thyroxine (FT4) but a reportedly normal TSH concentration. Both patients had prominent adrenergic symptoms, unilateral thyroid tenderness, raised erythrocyte sedimentation rate (ESR), and sinus tachycardia. They were treated with propranolol and prednisolone, with marked clinical improvement and subsequent biochemical recovery. These cases highlight the importance of integrating the clinical phenotype with thyroid-function testing and considering assay-related, physiological, and analytical explanations when the TSH concentration appears discordant with the FT4 concentration.