Non-pituitary GH regulation of the tissue microenvironment.

Non-pituitary growth hormone (npGH) expression is well established in extrapituitary tissues, but an understanding of the physiological role of npGH remains rather limited. Pro-tumorigenic npGH impacting the tumor microenvironment has been reviewed. We focus here on autocrine/paracrine npGH effects in non-tumorous tissues and discuss its mechanisms of action in the normal tissue microenvironment. We address the tissue-specific effects of npGH in regulating stem, endothelial, immune, and epithelial cells and highlight the related role of npGH-associated changes in tissue aging.