Which thyroid condition is associated with a 'thyroid inferno' on Doppler ultrasound?

• A. Hashimoto's thyroiditis
• B. Subacute thyroiditis
• C. Graves disease
• D. Anaplastic thyroid cancer

Answer: (D)

The pattern being tested is the Doppler vascular signature of active Graves disease. In Graves, autoimmune stimulation of the TSH receptor causes diffuse enlargement and markedly increased blood flow throughout the gland. On color Doppler, this appears as widespread, intense red signal across the thyroid—an effect often described as a thyroid inferno. This high, diffuse vascularity reflects the gland’s hyperfunction and angiogenesis, which matches the hyperthyroid state.

Hashimoto’s thyroiditis can show a more heterogeneous gland with variable vascularity, but it is not characterized by the global, exuberant hyperemia seen in Graves. Subacute thyroiditis typically shows reduced vascularity because the gland is inflamed and disrupted, not hyperactive. Anaplastic thyroid cancer presents as a focal, often rapidly enlarging mass with irregular margins and variable, usually not diffuse hypervascularity; it does not produce the diffuse inferno pattern.

So the presence of a thyroid inferno on Doppler most strongly points to Graves disease due to its diffuse hypervascular, hyperfunctioning state.