Growth Factors

Abstract

For children in whom decreased growth velocity raises suspicion for possible growth hormone (GH) deficiency, the next step in evaluation is typically measurement of insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 3 (IGFBP-3). These are initially measured in lieu of GH itself because GH is pulsatile and measurement of random GH levels is not clinically useful. In contrast, both IGF-1 and IGFBP-3 have longer half-lives and relatively stable levels in circulation. Both are made in the liver in response to GH and thus serve as moderately good proxies for GH levels. Measurement of IGF-1 and IGFBP-3 in the primary care setting may be helpful in the initial evaluation of short stature and/or poor growth velocity. Robust IGF-1 and IGFBP-3 levels decrease suspicion for GH deficiency, whereas relatively low or low-normal levels may raise suspicion in the context of poor growth velocity. In the latter case, a GH stimulation test is often performed as the next step in evaluation. This chapter discusses the use of IGF-1 and IGFBP-3 in the primary care setting and briefly reviews growth hormone stimulation testing, which is performed by pediatric endocrinologists.