Transient thyrotoxicosis associated with acute hemorrhagic infarction of autonomously functioning thyroid nodules.

Two patients with nontoxic autonomously functioning thyroid nodules had transient hyperthyroidism after acute hemorrhagic infarction. Previously solid "hot" nodules were converted to cystic "cold" nodules. Aspiration confirmed the hemorrhagic nature of the process. There was marked regression in nodule size, marked reduction of nodular autonomous secretory activity (indicated by a change from a blunted to a normal response to thyrotropin-releasing hormone), and spontaneous recovery of function in the previously suppressed extranodular thyroid tissue. Confusion of this entity with a nontoxic autonomously functioning thyroid nodule that has progressed to the toxic stage may be avoided if the loss of nodular function is noted on imaging. The possibility of granulomatous thyroiditis may be excluded by blood aspiration.