EFFECTS OF SUMATRIPTAN ON GROWTH HORMONE RELEASING HORMONE-STIMULATED GROWTH HORMONE SECRETION IN ACROMEGALY

: Sumatriptan (SU), a specific 5-HT1D receptor agonist, was recently shown to be able to increase growth hormone (GH) levels in normals, but not in acromegalics, while no effect was seen on prolactine (PRL). SU is also able to produce an increase in GH response to growth hormone releasing hormone (GHRH) in prepubertal children. In this study we investigated whether SU administration influences GHRH-induced GH secretion in 8 acromegalics, and 6 age-matched normal volunteers, as a control group. We evaluated the effects of SU (6 mg s.c.) or placebo (PL) administration on GHRH (1 microgram/kg bw i.v.)-induced GH and PRL secretion. After SU priming the GH response to GHRH did not changed in acromegalics, but significantly decreased in controls, in comparison with that observed after PL plus GHRH. In acromegalics, no difference in GH peak was seen after SU plus GHRH and PL plus GHRH, nor was any difference seen in AUC between tests. In controls, no difference was seen in GH peaks, while SU priming significantly (P < 0.03) decreased the AUC 90-120 min of GH after GHRH administration. In acromegalics, SU did not change the slight GHRH-induced increase in PRL levels. Our study documents that 5-HT1 D receptors do not interfere with GHRH-stimulated GH secretion in acromegalic subjects. In normals, SU is able to decrease GH response to GHRH, thus confirming that 5-HT1D receptors are able to modulate GH secretion in normals.