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Physiology of insulin-like growth factor-1

David R Clemmons, MD
Section Editor
Peter J Snyder, MD
Deputy Editor
Kathryn A Martin, MD


Insulin-like growth factor-1 (IGF-1) is a hormone that functions as the major mediator of growth hormone (GH)-stimulated somatic growth, as well as a mediator of GH-independent anabolic responses in many cells and tissues. IGF-1 is a small peptide (molecular weight 7647) that circulates in serum bound to high affinity binding proteins. IGF-1 is an unusual peptide in this regard since it is more than 99 percent protein-bound.

IGF-1 is synthesized by multiple mesenchymal cell types. As a result, there are two major mechanisms of IGF-1 regulation:

IGF-1 that is synthesized in the liver and secreted into the blood is under the control of GH.

Autocrine/paracrine IGF-1 synthesized in peripheral tissues, such as bone. Its synthesis is controlled by GH and by factors that are secreted locally by the surrounding cell types. Some of the secreted autocrine/paracrine IGF-1 enters into the systemic circulation. Therefore, understanding the regulation of autocrine/paracrine synthesis of IGF-1 is necessary to interpret changes in serum IGF-1 concentrations.

IGF-1 exerts its effects via activation of the IGF-1 receptor [1]. This receptor is widely distributed, which enables blood-transported IGF-1 to coordinate balanced growth among multiple tissues and organs. In contrast, autocrine/paracrine IGF-1 can stimulate local, unbalanced growth independently of systemic GH. Examples of this type of growth regulation are wound healing and growth of the contralateral kidney after unilateral nephrectomy.

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Literature review current through: Nov 2017. | This topic last updated: Oct 03, 2017.
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