The association of growth hormone parameters with skeletal muscle phosphocreatine recovery in adult men.

Abstract

Previous studies have suggested a relationship between GH and mitochondrial function. However, little is known about the relationship of specific GH indices and in vivo measures of mitochondrial function in humans. The objective of this study was to determine the association between GH, IGF-I, and phosphocreatine (PCr) recovery, a measure of mitochondrial function, in otherwise healthy adults. Thirty-seven healthy men and women were studied at a single university medical center. Subjects underwent GH stimulation testing with GH releasing hormone-arginine and measurement of IGF-I. Mitochondrial function was determined by PCr recovery after submaximal exercise by (31)Phosphorous magnetic resonance spectroscopy. Subjects underwent assessment of lean and fat mass with use of dual energy X-ray absorptiometry. There were no differences in PCr recovery between men and women (men 20.7±1.5 vs. women 24.8±1.4 mM/min; P > 0.05). IGF-I (r = 0.33; P = 0.04) was associated with PCr recovery in all subjects. Among men, IGF-I (r = 0.69; P = 0.003), peak stimulated GH (r = 0.52; P = 0.04), and GH area under the curve (AUC) (r = 0.53; P = 0.04) were significantly associated with PCr recovery. However, neither IGF-I, peak stimulated GH, nor GH AUC (all P > 0.05) were associated with PCr recovery in women. After adjusting for age, race, and physical activity, IGF-I remained significantly associated with PCr recovery (β = 0.10; P = 0.02) among men. IGF-I, peak stimulated GH, and GH AUC are associated with skeletal muscle PCr recovery in men.