TSH-secreting pituitary macroadenoma: rapid tumor shrinkage and recovery from hyperthyroidism with octreotide

A 44-year-old man with atrial fibrillation caused by hyperthyroidism is described. The underlying disease was a TSH-secreting macroadenoma of the pituitary. Treatment with the somatostatin analog octreotide eliminated hyperthyroidism and atrial fibrillation within 4 days and the tumor size diminished substantially within 3 weeks.