Abstract
The aim of the present study was to ascertain if reduced central serotoninergic activity might contribute to the well-known blunted growth hormone (GH) response to GH-releasing hormone (GHRH) in obese patients. Thus, we studied the effect of prolonged stimulation of the serotoninergic system by fenfluramine (FF; 60 mg twice daily for 7 days) on GHRH-induced GH release in nine obese and seven normal subjects. In controls, GHRH (100 μg intravenously [IV]) injection increased GH levels from 2.3 ± 1.8 (±SE) to 18.5 ± 2.8 mU/L, P < .002. FF administration enhanced both basal and GHRH-stimulated GH levels (peak, 38.4 ± 8.3 v 6.9 ± 2.6 mU/L, P < .002). This response was significantly higher ( P < .02) than in pretreatment. In obese patients, GH responsiveness to GHRH was slight (peak, 7.1 ± 2.0 v 0.6 ± 0.18 mU/L, P < .01) and lower ( P < .01) than in controls. FF administration did not affect this response. In controls, the enhanced FF-induced GH release after a maximal dose of GHRH indicates that serotoninergic activation influences GH secretion and that the mechanism involved is independent of endogenous GHRH. In obese patients, we found a blunted GH responsiveness to GHRH that was not affected by FF, thus supporting the hypothesis that the serotoninergic control on GH release is impaired.
Published Version
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