title: 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.
authors.affiliation: Military Performance Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760, USA. bradley.nindl@us.army.mil
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Nindl
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Rarick
authors.forename: John W
authors.initials: JW
authors.lastname: Castellani
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Tuckow
authors.forename: John F
authors.initials: JF
authors.lastname: Patton
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Young
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Montain
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D005080:Exercise Test; D013006:Growth Hormone / Q000097:blood* / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood* / Q000378:metabolism; D008297:Male; D008889:Military Personnel; D010807:Physical Endurance; D005082:Physical Exertion; D012892:Sleep Deprivation / Q000097:blood* / Q000503:physiopathology*
chemical_list: D007334:Insulin-Like Growth Factor I; D007986:Luteinizing Hormone; D013006:Growth Hormone