DESENSITIZATION TO SOMATOSTATIN ANALOG (OCTREOTIDE) OBSERVED IN A PATIENT WITH ACROMEGALY

We encountered a 33-year-old female patient with a pituitary growth ho rmone (GH)-secreting macroadenoma. The patient was treated with somato statin analogue (Octreotide) in combination with bromocriptine for 2 m onths before a transsphenoidal adenomectomy was carried out. Octreotid e(300-800 mu g/day) in combination with bromocriptine was effective in reducing the size of the adenoma by 36%, but produced only a marginal decrease in serum GH. After the operation, bromocriptine alone (15 mg /day) did not lower the level of GH which was produced by residual ade noma tissue. When octreotide (200 mu g/day) was resumed along with the bromocriptine one year after the operation, it effectively lowered se rum GH for 6 months. Thereafter, octreotide therapy became ineffective with a concomitant rise in serum GH and somatomedin C, which was not accompanied by an increase in tumor size. This was a rare case of acro megaly that showed desensitization to octreotide after long-term treat ment.