TY - CHAP M1 - Book, Section TI - Mechanisms of Hormone Action A1 - Grimberg, Adda A1 - DiMeglio, Linda A. A2 - Kline, Mark W. PY - 2018 T2 - Rudolph's Pediatrics, 23e AB - Hormones are molecules secreted into the circulation to influence the function of target cells in another tissue or organ. In addition to distant targets via the circulation (endocrine action), many hormones also influence the function of the cells that secreted them (autocrine action) or that of adjacent cells (paracrine action). For example, when insulin, produced by pancreatic beta cells, stimulates glucose storage and oxidation, protein synthesis, and lipid storage in the liver, muscle, and fat, it is acting in an endocrine fashion; when it inhibits glucagon secretion by the nearby pancreatic alpha cells, it is acting in a paracrine fashion. Frequently, the endocrine and autocrine/paracrine actions of a hormone lead to the same effect. For example, growth hormone (GH) stimulates hepatic production of insulin-like growth factor I (IGF-I), the main mediator of somatic growth in childhood. Mice with targeted hepatic deletion of IGF-I expression grow to normal size, despite a 75% reduction in circulating IGF-I concentrations. This seminal experiment demonstrated the importance of autocrine and paracrine IGF-I production by other tissues to body growth. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/04/24 UR - accesspediatrics.mhmedical.com/content.aspx?aid=1182918332 ER -