Toxic hematoma: an unusual and previously undescribed type of thyrotoxicosis.

The present case describes a new and unusual variant of thyrotoxicosis: transient hyperthyroxinemia following acute and massive hemorrhage into a previously normal thyroid gland. A 74-year-old woman presented with a large painful neck mass, palpitations, rapid atrial fibrillation, and hyperthyroxinemia following a fall and neck trauma while treated with excessive oral anticoagulants. Ultrasound and computerized tomography of the neck were consistent with a massive intrathyroidal hematoma. Elevation in serum T4 and T3 levels with suppressed TSH normalized over 3-4 weeks in parallel with hematoma shrinkage. Her tests were consistent with extensive bleeding into thyroidal tissue producing release of stored hormone. Her clinical course was compatible with the known disappearance rate of thyroxine and she returned to her euthyroid status without antithyroid therapy.