Figure 1.

Alterations in somatotropic signaling caused by DR. Decreased food intake is sensed by the hypothalamus leading to diminished release of growth hormone releasing hormone (GHRH). This signals to the pituitary to secrete less growth hormone (GH). GH-responsive cells in the liver then synthesize lower amounts of insulin-like growth factor (IGF)-1, which results in lower negative feedback to the hypothalamus to regulate GHRH release. Perhaps in an indirect manner, GH causes increased insulin sensitivity and decreased insulin production from pancreatic islet cells. Although the direct and/or indirect effects on reproduction remain unclear, the changes in somatotropic signaling from DR leading to increased insulin sensitivity and reduced oxidative stress might be the mechanism whereby DR delays senescence [14,16].