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-I (IGF-I) and testosterone, respectively. This study examined the hypothesis that 84 hrs of sustained physical exertion with caloric and sleep restriction alters the secretion of GH and LH. 10 male soldiers (22 SD 3 yr, 183 SD 7 cm, 87 SD 8 kg) had blood drawn overnight from 1800 hr to 0600 hr every 20 min for GH, LH and leptin and every 2 hrs for IGF-I (total and free), IGF binding proteins (BPs) 1 and 3, testosterone (total and free), glucose, and free fatty acids during a control week (C) and after 84 hr of military operational stress. Time-series cluster and deconvolution analyses assessed the secretion parameters of GH and LH. Significant results (p0.05) 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 (~50%) and overnight pulsatile secretion (~50%), IGFBP-1 (+67%) and free fatty acids (+33%) increased, while leptin (-47%), total (-27%) and free IGF-I (-32%), total (-24%) and free testosterone (-30%), and IGFBP-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.