Altered secretion of growth hormone and luteinizing hormone after 84 h of sustained physical exertion superimposed on caloric and sleep restriction

Abstract

The pulsatile release of growth hormone (GH) and luteinizing hormone (LH) from the anterior pituitary gland is integral for signaling secretion of insulin-like growth factor (IGF)-I and testosterone, respectively. This study examined the hypothesis that 84 h of sustained physical exertion with caloric and sleep restriction alters the secretion of GH and LH. Ten male soldiers [22 yr (SD 3), 183 cm (SD 7), 87 kg (SD 8)] had blood drawn overnight from 1800 to 0600 every 20 min for GH, LH, and leptin and every 2 h for IGF-I (total and free), IGF binding proteins-1 and -3, testosterone (total and free), glucose, and free fatty acids during a control week and after 84 h of military operational stress. Time-series cluster and deconvolution analyses assessed the secretion parameters of GH and LH. Significant results (P < or = 0.05) were as follows: body mass (-3%), fat-free mass (-2.3%), and fat mass (-7.3%) declined after military operational stress. GH and LH secretion burst amplitude (approximately 50%) and overnight pulsatile secretion (approximately 50%), IGF binding protein-1 (+67%), and free fatty acids (+33%) increased, whereas leptin (-47%), total (-27%) and free IGF-I (-32%), total (-24%) and free testosterone (-30%), and IGF binding protein-3 (-6%) decreased. GH and LH pulse number were unaffected. Because GH and LH positively regulate IGF-I and testosterone, these data imply that the physiological strain induced a certain degree of peripheral resistance. During periods of energy deficiency, amplitude modulation of GH and LH pulses may precede alterations in pulse numbers.

Effects of 24-hour Food Restriction on Plasma Human Growth Hormone, IGF-1, Cortisol and Testosterone Responses in Resistance Exercise

“…It has, also, been shown that weight reduction may lead to alterations in lipid profile, as it is the case in our study, which may be the consequence of the increased hormonal responses to the exercise. Our data are in agreement with previous studies that showed an increase in testosterone and cortisol immediately after exercise [4,31]. However, Opstad [32] and Axelsson et al [33] found no change in cortisol concentrations.…”

“…Nindl et al [31] observed that brief periods of intense physical activity superimposed on energy and sleep restriction induced amplifications in GH and LH secretions. However, due to methodological differences such as exercise type (e.g., intensity and duration) or sleep loss protocol, the present study's results cannot be compared with those of previous investigations.…”

Serum Sex Hormone–Binding Globulin and Cortisol Concentrations are Associated With Overreaching During Strenuous Military Training

“…Furthermore, basal serum cortisol decreased with a concomitant increase in the number of subjects who felt overloaded. Previously, serum total testosterone concentration has been shown to decrease in response to demanding training periods (6,37), as well as during extremely stressful military training periods (25,26), and to increase with overload training (36). In contrast to the present study, basal SHBG has been found to increase (19,23) and IGF-1 to decrease (23-26) after heavy training.…”

“…This may be a marker of overtraining, along with lower psychosocial stress (29,31,33,37). Basal serum cortisol has been found to increase during extremely stressful military training periods (25,26), but no change (6,19,36), or a decrease (29,31) has been observed in endurance based overtraining studies.…”

Utility of circulating IGF-I as a biomarker for assessing body composition changes in men during periods of high physical activity superimposed upon energy and sleep restriction

“…While these conventional nutritional biomarkers have their utility, they are limited by their relatively long half-lives (2-20 days) and can be affected by nonnutritional factors (18,25). Unlike many hormones used as biomarkers of nutritional/metabolic status, such as growth hormone (GH), IGF-I concentrations exhibit minimal circadian variability through the day (26); therefore, single time samples are valid indicators of IGF-I status.…”