A rare case and a rapid tumor response to therapy: dramatic reduction in tumor size during octreotide treatment in a patient with TSH-secreting pituitary macroadenoma.

Thyrotropin (TSH)-secreting pituitary adenomas are the less frequent form of presentation of pituitary tumors. The presence of somatostatin receptors on TSH-secreting adenomas allows treatment of central hyperthyroidism with somatostatin analogs. We report a 21-yr-old woman with TSH-secreting pituitary macroadenoma, who was diagnosed based on the symptoms of hyperthyroidism, the lack of inhibition of serum TSH despite an increased serum free thyroxine (FT4), a low response of serum TSH to thyrotropin-releasing hormone, and a pituitary tumor as revealed by magnetic resonance imaging. The treatment with the somatostatin analog octreotid resulted in inhibition of serum TSH and FT4 to euthyroid levels with concomitant clinical improvements such as the disappearance of sweating, tachycardia, and finger tremors within 7 d. The tumor size diminished dramatically within 6 wk during treatment of one monthly im injection of 20 mg octreotide-LAR. These effects were continued over 2 yr after the start of octreotide-LAR therapy. Therefore, octreotide-LAR appears to be a useful therapeutic tool to facilitate the medical treatment of TSH-secreting pituitary tumors.