Effect of octreotide on glucose tolerance in acromegaly.

To determine the effect of the somatostatin analog octreotide on glucose tolerance in acromegaly, we examined glucose profiles, oral glucose tolerance and the insulinogenic index in patients treated with this analog. Ninety patients participated in a long-term, prospective, open-label study. There was no significant change between mean daily blood glucose profiles at baseline or during octreotide treatment. Using glucose tolerance test criteria, 61% of 90 patients had normal baseline glucose tolerance. While on octreotide, 20% and 29% of these patients, respectively, developed impaired glucose tolerance or became frankly diabetic. Conversely, three of the patients who were diabetic at baseline (N = 11) became normal (18%) or developed impaired glucose tolerance (9%) during octreotide therapy. There was no relationship between the dose of octreotide and change in glycemic state. The insulinogenic index (insulin/glucose) response to a glucose challenge decreased uniformly in octreotide-treated patients. Female patients and those with elevated baseline insulin levels were more likely to develop diabetes mellitus during octreotide therapy. In conclusion, octreotide significantly alters glucose tolerance in patients with acromegaly, mandating glucose monitoring during this form of therapy.