Evidence for involvement of endogenous somatostatin in the galanin-induced growth hormone secretion in children

We have evaluated the effects of the combined administration of Galanin (Gal) plus growth hormone-releasing hormone (GHRH) and of pyridostigmine (PD), a cholinergic agonist, plus Gal on GH secretion in 15 children (12 males and three females, age 7.7-14.5 y) with short stature. Children were subdivided into two groups. In group 1 (n = 7) Gal (15 µg/kg h i.v.) plus GHRH (1 µg/kg i.v.) administration induced a higher GH rise (peak = 73.1 ± 10.2 ng/mL, mean ± SD; area under the curve (AUC) = 531.9 ± 78.7 ng-min-mL-1) than did GHRH alone (peak = 38.9 ± 26.5 ng/mL, p < 0.05; AUC = 256.9 ± 165.6 ng/mL/min-1, p < 0.005). Gal had a synergistic effect on the GHRH-induced GH response because the GHRH plus Gal AUC response was significantly higher (p < 0.01) than the sum of the areas of response to GHRH and Gal alone. In group 2 (n= 8) PD administration (60 mg/kg p.o.) had no significant effects on the Gal-induced GH secretion (peak = 14.9 ± 8.8 and 16.0 ± 9.8 ng/mL after Gal and PD + Gal, respectively; AUC = 91.2 ± 52.1 and 125.2 ± 83.6 ng mL min-1 after Gal and PD + Gal, respectively). Our results confirm the ability of Gal to stimulate GH secretion in children, and strengthen the view that its mechanism of action involves modulation of endogenous somatostatin release.