The effect of galanin on growth hormone secretion in children of normal and short stature

We have evaluated the effect of galanin (Gal), a newly identified hypothalamic peptide, on growth hormone (GH) secretion in 10 children with normal stature (NS), nine with constitutional growth delay (CGD), and five with isolated GH deficiency (IGHD). Gal was infused intravenously at a rate of 8 or 15 μg/kg/h. All children also underwent an acute oral clonidine test (0.15 mg/m2). In CGD children the mean plasma GH peak after 8 μg/kg/h of Gal infusion (13.3 ± 1.7 ng/mL; mean ± SEM) was higher (p < 0.02) than in NS children (8.5 ± 0.8 ng/mL). When the dose of Gal was increased to 15 μg/kg/h the mean plasma GH peak in CGD children (18.5 ± 3.5 ng/mL) was still higher than in the NS group (13.2 ± 2.9 ng/mL), although not significantly so. In IGHD children the mean plasma GH peak elicited by 8 or 15 μg/kg/h of Gal (3.8 ± 0.7 and 3.9 ± 0.5 ng/mL, respectively) was lower than that obtained in either CGD (p < 0.0002) or NS children (p < 0.001). In NS children the mean plasma GH peak after acute clonidine administration (22.3 ± 3.0 ng/mL) was higher than that observed after either dose of Gal used (p < 0.001 and p < 0.05 with 8 and 15 μg/kg/h, respectively). In CGD or IGHD children mean plasma GH peak after acute clonidine (14.8 ± 2.6 and 4.1 ± 1.2 ng/mL, respectively) was not significantly different from that observed after either dose of Gal. No correlation was found between peak plasma GH responses to clonidine and to Gal infusion at either dose used. Gal infusion did not cause any significant change in LH, FSH, prolactin, and TSH plasma levels. We conclude that Gal stimulates GH secretion in CGD as well in NS children but not in children with isolated GH deficiency. Gal, at least under our experimental conditions, does not seem to be of help in the differential diagnosis of children with short stature.