EFFECTS OF SEX AND AGE ON THE GROWTH-HORMONE RESPONSE TO GALANIN IN HEALTHY-HUMAN SUBJECTS

The aim of our study was to analyze the effects of sex an age on the G H response to galanin infusion in healthy subjects. We have studied 12 young (age, <40 yr) nonobese healthy volunteers [6 females: age, 31.0 +/- 2.5 yr; body mass index (BMI), 21.6 +/- 0.9 kg/m2; 6 males: age, 29.2 +/- 1.4 yr; BMI, 23.3 +/- 0.4 kg/m2] and 11 old (age, >65 yr) hea lthy subjects (5 females: age, 83.8 +/- 3.8 yr; BMI, 23.4 +/- 1.4 k g/ M2; 6 males: age, 79.7 +/- 4.6 yr; BMI, 23.3 +/- 0.2 kg/m2). All subje cts received an infusion of synthetic porcine galanin (500 mug, iv) in 100 mL saline from 0-45 min. Blood samples for GH measurement were dr awn at -15, 0, 15, 30, 45, 60, 90, and 120 min. The GH peaks after gal anin treatment in young females (11.9 +/- 2.9 mug/L) were significantl y (P < 0.05) higher than those in the young males (5.1 +/- 1.8 mug/L). Old males showed significantly higher peak GH levels after galanin tr eatment (8.6 +/- 3.1 mug/L) than old females (2.4 +/- 0.6 mug/L). The GH peaks and areas under the curve after galanin treatment were signif icantly (P < 0.05) higher in young than in old females. On the contrar y, no significant differences were observed after galanin treatment in young and old males. The magnitude of galanin-induced GH secretion si gnificantly correlated with estradiol levels in young women. Our data seem to suggest that circulating estrogen levels play a crucial permis sive role in galanin-induced GH secretion in humans.