RELATIONSHIP BETWEEN NOCTURNAL GROWTH HORMONE RELEASE AND BODY COMPOSITION IS MATURATION DEPENDENT 64

Abstract

We examined the relationship between gender, percent body fat (% fat) and 12-hour growth hormone (GH) release in healthy children and adolescents. The sample included 25 boys and 23 girls in Tanner genital stages (G) 1 through 4. The sample was divided as follows: boys G1+G2=19, G3+G4=6; girls G1+G2=8, G3+G4=15. Body composition was measured by underwater weighing using age-related density corrections. Blood samples were withdrawn every 10 min from 1800 h to 0600 h to determine the mean nocturnal serum GH concentration. The data (mean ± SE) are: Table. Two-way ANOVA showed no gender by maturation interactions. As expected, the boys and girls in G3+G4 were older, taller, and heavier than in G1+G2. As a group, the girls had a higher% fat than the boys. Significant inverse relationships existed between mean GH concentration and% fat for the G1+G2 boys (r = -0.49, p<0.05) and G1+G2 girls (r = -0.73, p < 0.05), but not for the G3 + G4 boys (r = -0.07) and G3+G4 girls (r = 0.05). Conclusion: Pre- and early-pubertally adiposity and GH release are inversely related and the relationship appears to be stronger in females than males. During mid- and late-puberty the relationship is much weaker. Gender and maturational differences in GH release may be due to changes/differences in intra-abdominal visceral fat, insulin resistance, and an over-riding effect of gonadal steroids during puberty.