Figure 1.

GH–IGF1 axis and actions in bone, muscle and body metabolism. GH secretion is regulated by three peptides: GH-releasing hormone (GHRH), ghrelin-stimulating GH release and somatostatin (SS)-inhibiting GH release. In circulation, GH stimulates the liver and other peripheral tissues to produce insulin-like growth factor-1(IGF1). GH/IGF1 stimulates longitudinal growth, enhances bone mass, and regulates bone metabolism. GH promotes the positive protein balance in skeletal muscle and has lipolytic effects which may play a role in maintaining glucose homeostasis with decreased insulin sensitivity which all promote cardiovascular system (CVS) functional capacity and maximal oxygen consumption (VO₂ max).