The impact of sex and exercise duration on growth hormone secretion

Abstract

Previous research clearly indicates a linear relationship between exercise intensity and growth hormone (GH) release and that this relationship is influenced by sex. The present study examined the GH response to increasing exercise duration in young men and women. Fifteen healthy subjects (8 men and 7 women) completed three randomly assigned exercise sessions (30, 60, and 120 min) at 70% of peak oxygen consumption. Blood samples were collected every 10 min beginning 30 min before exercise, for a total of 240 min. Total integrated GH concentration (IGHC) increased with increasing exercise duration for men and women (601, 1,394, and 2,360 microg/l.4 h; 659, 1,009 and 1,243 microg/l.4 h for 30, 60, and 120 min of exercise, respectively). Regression analysis revealed that IGHC (logarithmically transformed) was significantly influenced by exercise duration (logarithmically transformed) (120 min > 60 min > 30 min) and that a significant sex-dependent effect was present even after adjustments for fitness level and percent body fat (men > women). The slope of the regression line was greater for men than for women (1.003 vs. 0.612; P = 0.013), but the average height of the regression line was greater for women (7.287 vs. 6.595; P < 0.001). Although GH secretory pulse half-duration was greater in women (P = 0.001), and GH half-life was greater in men (P = 0.001), they were not affected by exercise duration. The total mass of GH secreted during exercise increased with exercise duration (P < 0.001) but was not affected by sex (P = 0.137). Results from the present investigation indicate that when exercise intensity is constant, exercise duration significantly increases IGHC and that this relationship is sex dependent.

The GH-IGF-I Response to Typical Field Sports Practices in Adolescent Athletes: A Summary

“…Interestingly, these gender differences disappeared when endurance exercise was performed intermittently (23), and were diminished with age (22). In contrast, when exercise intensity remains constant, exercise duration significantly increases integrated GH concentration in male more than females (24). Only a single study examined the effect of 3 30-s sprints with 20-min rest between the sprints on GH secretion in active men and women.…”

Effects of long-term continuous positive airway pressure on body composition and IGF1

“…First, ventilated patients report less daytime sleepiness and more vitality (46), which may impact upon their level of physical activity and protect against the disease (47). In addition, physical activity augments GH axis activity in young and to a lesser extent in older persons (48,49). Thus, exercise-induced increases in GH axis activity may have additional beneficial effects on LBM.…”

The Growth Hormone/Insulin-Like Growth Factor-I Axis in Exercise and Sport

“…Deconvolution analysis revealed that increased GH levels resulted from an increase in the mass of GH secreted per pulse, with no change in pulse frequency or the half-life of elimination. Later studies from the same laboratory demonstrated that GH secretion correlates positively with duration of exercise when intensity is constant (145), is augmented by (122) compared GH secretion at rest and during exercise in men and women matched for age and physical fitness and demonstrated that GH secretion rates under resting conditions were greater in women; but during exercise, although absolute GH secretion rates were also increased, the increment from baseline was similar in men and women and did not correlate with sex hormones. This finding was confirmed in a later study (123).…”

“…The neuroendocrine pathways through which GH secretion is regulated during exercise are complex and poorly understood, but there is evidence that adrenergic, cholinergic, and opioid pathways are involved (89). The magnitude of the GH response to exercise is influenced by age (118 -120), gender (121)(122)(123), body composition (124 -126), physical fitness (118,120,127,128), and the intensity (114, 127, 129 -133), nature (134 -142), and duration (130,(143)(144)(145) of exercise ( Table 4). The impact of these variables has been more clearly defined in a recent series of meticulously carried out studies using ultrasensitive chemiluminescence GH assays and deconvolution analysis of GH secretion.…”