Thyrotropin secreting pituitary adenoma effectively treated with octreotide

We report a 65-year-old woman with thyrotropin (TSH) secreting pituitary adenoma, who was diagnosed based on the lack of inhibition of serum TSH despite an increased serum free thyroxine (T4), a low response of serum TSH to thyrotropin releasing hormone, and a pituitary tumor as revealed by magnetic resonance imaging. The pituitary adenoma was, however, inoperable due to chronic respiratory failure. The treatment with octreotide in a dose of 100 microg b.i.d. resulted in inhibition of serum TSH and free T4 to euthyroid levels and considerable shrinkage of the pituitary tumor. These effects were continued over 8 months after the start of octreotide therapy without any adverse effects. These findings add further evidence that octreotide is useful for treating inoperable TSH secreting pituitary adenoma.