What Are the Key Symptoms of Subacute Thyroiditis?

Subacute thyroiditis—also known as de Quervain thyroiditis—is an inflammatory condition of the thyroid gland typically triggered by a viral infection. It presents with a characteristic triphasic clinical course: an initial thyrotoxic phase marked by neck pain, tenderness over the thyroid gland, low-grade fever, fatigue, and symptoms of hyperthyroidism—including palpitations, tremor, weight loss, and anxiety. This phase reflects the release of preformed thyroid hormones from damaged follicular cells.

As inflammation progresses, patients often transition into a euthyroid phase, during which thyroid function tests normalize and symptoms may temporarily subside. This is frequently followed by a transient hypothyroid phase—particularly in individuals with underlying autoimmune susceptibility—characterized by fatigue, cold intolerance, constipation, dry skin, and mild weight gain. Most patients recover spontaneously within several months, with thyroid function returning to baseline and no permanent gland damage.

Diagnostic clues include elevated erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP), suppressed serum TSH, elevated free T4 and T3 early on, and a markedly reduced radioactive iodine uptake on thyroid scintigraphy—distinguishing it from Graves’ disease. Neck ultrasonography may reveal heterogeneous echotexture and reduced vascularity. Clinical suspicion should be high in patients presenting with acute anterior neck pain and systemic symptoms following an upper respiratory tract infection.