EFFECT OF OCTREOTIDE ON GROWTH HORMONE SECRETION IN PATIENTS WITH ACROMEGALY

SUMMARY • A majority of growth hormone secreting pituitary adenomas respond well to soma-tostatin and somatostatin analogues. The acute action of octreotide, a synthetic somatostatin ana-logue, on growth hormone secretion was assessed in 42 patients with clinically and laboratory veri-fied acromegaly. Octreotide was administered subcutaneously in a dose of 50 µg. Blood sampling was performed at 1-hour intervals during 6 hours of testing. The mean basal values of growth hor-mone (χ±SE) was 26.3±4.5 ng/ml (range 6.1-66.6 ng/ml), and of IGF-I 2940±171.7 IU/l (range 2350-4856 IU/l). Reduction in growth hormone values below 5 ng/ml was recorded in 31 (73.8%), suppression by more than 50 % in 5 (11.9%) and by more than 45 % in 3 (7.1%) patients. Maximal suppression was noticed in the first two hours of testing. In 3 (7.1%) patients, resistance to octreotide with no change in growth hormone values was observed. In conclusion, octreotide reduces growth hormone values in most acromegalic patients. A small proportion of acromegalic patients do not respond well to octreotide, probably due to the lack of somatostatin receptors on tumor cells. We consider the acute octreotide test as a very useful tool in triage of acromegalic patients eligible for medicamentous treatment