%0 Journal Article
%T Effects of a single dose of N-Acetyl-5-methoxytryptamine (Melatonin) and resistance exercise on the growth hormone/IGF-1 axis in young males and females
%A Erika Nassar
%A Chris Mulligan
%A Lem Taylor
%A Chad Kerksick
%A Melyn Galbreath
%A Mike Greenwood
%A Richard Kreider
%A Darryn S Willoughby
%J Journal of the International Society of Sports Nutrition
%D 2007
%I BioMed Central
%R 10.1186/1550-2783-4-14
%X Growth hormone is secreted from the adenohypohysis of the pituitary gland and is regulated by a final common pathway, consisting of inhibitory control of somatostatin (SST) and stimulatory control of hypothalamic GH-releasing hormone (GHRH). As such, GH is known to display profound anabolic effects at the tissue level and has been implicated to play a significant role in metabolic regulation, protein synthesis, and cell multiplication and differentiation in skeletal muscle. Once secreted into the circulation, free, unbound GH has a half-life of approximately nine minutes [1]. Almost 50% of GH in circulation is bound to a high-affinity GH binding protein (GHBP), and GHBP seems to directly correlate with tissue GH receptor content [2]. However, it is the free, unbound GH that is able to bind to the extracellular domain of the GH receptor, thereby effecting GH kinetics which can invariably regulate growth factor release and GH signaling in skeletal muscle. Relative to skeletal muscle, the anabolic role of GH is based on the circulating levels of free GH and exists due to its influence on the activity of various growth factors such as insulin-like growth factor 1 (IGF-1).The majority of GH secretion from the pituitary is controlled by hormonal signals received from the hypothalamus. In addition, GH release can also be regulated at the hypothalamic level by various metabolic stress signals such as acute resistance exercise. The release of GH has been shown to occur in response to single bouts of resistance exercise. A single bout of resistance exercise at 85% of the one-repetition maximum (1-RM) was shown to significantly elevate serum GH [3]. Also, when compared to a single set of high-intensity resistance exercise at 90% 1-RM, a single set of low- and moderate-intensity resistance exercise at either 50% or 70% 1-RM immediately following high intensity exercise resistance exercise at 90% 1-RM produced greater increases in serum GH levels [4]. These data suggest that a h
%U http://www.jissn.com/content/4/1/14