Long term effects of continuous subcutaneous infusion of the somatostatin analog octreotide in the treatment of acromegaly

The marked pituitary tumor shrinkage achieved by continuous sc infusion (CSI) of the long-acting somatostatin analog octreotide in one acromegalic patient led us to treat 16 other acromegalic patients for up to 24 months by CSI. This therapy, given in doses ranging from 100-600 micrograms/day, resulted in normalization of the mean daily serum GH (mGH) and insulin-like growth factor I levels in 9 of the 17 patients (53%). In 7 patients, mean daily serum GH decreased but not to normal; 3 of these patients had hyperprolactinemia which was not influenced by octreotide. One patient was completely unresponsive. In contrast to the biochemical results, 80% of the patients had marked clinical improvement. Side-effects consisted of slightly impaired carbohydrate tolerance in 2 patients and cholelithiasis in 2 patients. Pituitary tumor size decreased in only 3 patients; in 1 of them visual field defects disappeared rapidly. These results suggest that octreotide treatment may prove beneficial before surgery in patients with macroadenomas, although its efficacy varies widely. Potential responsivity can usually be determined by a short course (24 h) of CSI of octreotide.