A 34-year-old woman develops severe pain over the front of her neck two weeks after a viral upper respiratory illness. The thyroid is firm and exquisitely tender. TSH is suppressed, free T4 is mildly raised, ESR is 70 mm/hour, and thyroid antibodies are negative. Which investigation best separates this condition from Graves disease?

• A Ultrasound showing increased vascularity of both lobes
• B Radioiodine uptake scan showing diffusely reduced uptake ✓
• C Fine needle aspiration showing follicular cells with nuclear grooves
• D CT neck showing retrosternal extension

Explanation

Subacute granulomatous (De Quervain) thyroiditis causes release of preformed hormone from destroyed follicles, producing thyrotoxicosis with a suppressed TSH, but inflamed follicular epithelium cannot trap iodine, so radioiodine uptake is strikingly low. In Graves disease the thyrotoxicosis arises from hormone synthesis driven by TSH receptor antibodies, giving diffuse increased uptake. Neck pain and a high ESR already favour thyroiditis, but the uptake scan is the definitive discriminator asked for here.

Reference: Williams Textbook of Endocrinology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.