OCTREOTIDE, BUT NOT BROMOCRIPTINE, INCREASES CIRCULATING INSULIN-LIKEGROWTH-FACTOR BINDING-PROTEIN-1 LEVELS IN ACROMEGALY

Twenty-three patients with active acromegaly underwent serum sampling for growth hormone (GH), insulin and insulin-like growth factor bindin g protein 1 (IGFBP-1) after placebo or single doses of octreotide or b romocriptine. Integrated 24-h serum GH levels decreased by 90% after o ctreotide and 49% after bromocriptine. A statistically significant cor relation between the course of GH levels after octreotide and bromocri ptine was observed (p < 0.001); Octreotide, but not bromocriptine, ind uced a significant increase in integrated 24-h serum IGFBP-1 levels to 37.4 times the baseline values. Bromocriptine caused a non-significan t increase in integrated 24-h serum IGFBP-1 levels, which argues again st a direct regulatory effect of GH on IGFBP-1 production in acromegal y. In conclusion, octreotide induces in acromegaly the production of I GFBP-1, which occurs independently of the number of somatostatin recep tors on the GH-secreting pituitary adenoma. The supposed inhibitory ef fect of IGFBP-1 on the biological effect of IGF-I might result in an a dditional clinical benefit in acromegalic patients as compared to trea tment directed at the pituitary level.