Relationship of physical exercise and ageing to growth hormone production

OBJECTIVE The normal decline in physiological function with ageing is assoc iated with a decrease in bioavailable growth hormone. Growth hormone has be en shown to alter body composition and increase fat-free mass in older men. Increased physical fitness is accompanied by an increase in 24-h growth ho rmone release. The purpose of this study was to examine the effect of exerc ise on declining growth hormone concentrations with increasing age. DESIGN AND PATIENTS The growth hormone production of 10 male subjects runni ng over 40 miles per week was compared to 10 healthy age-matched sedentary males (controls 57 +/- 2.8 vs, runners 60.5 +/- 3.4years). All subjects und erwent a basal assessment including a two-hour serum growth hormone profile followed by estimation of maximal exercise capacity on a cycle ergometer w ith growth hormone estimations at peak exercise activity and every five min utes whilst cycling at 40% of maximal exercise capacity. RESULTS Maximal exercise capacity confirmed the lifestyles of the two group s (VO2 max controls 22.36 +/- 6.05 vs, runners 34.91 +/- 13.13 l/min/kg, P= 0.01). The runners had lower body-mass indices than controls (BMI 22.3 +/- 1.5 vs. 25.5 +/- 2.0 kg/m(2), P=0.002). Peak growth hormone level during a two-hour resting profile was higher in the runners (median (range) controls 2.10 (0.20-12.20) vs, runners 5.25 (0.80-21.00) mU/I, P=0.03) as was the a verage growth hormone level during the two hour profile (mean growth hormon e per 2h median (range): controls 0.54 (0.03-4.88) vs, runners 2.17 (0.25-7 .45) mU/I, P=0.04). Growth hormone production at maximal exercise capacity was similar. Sex hormone binding globulin and testosterone were significant ly higher in the runners. CONCLUSIONS The results suggest that regular intensive exercise in older ma le subjects is associated with higher growth hormone and testosterone level s and that exercise may have a role in counteracting the normal decline in growth hormone with ageing.