Growth is stimulated and controlled by the anabolic and mitogenic activities of growth hormone (GH) and the insulin‑like growth factors (IGFs). Physiologically, hGH has general anabolic effects (i.e. increase of glucose uptake, protein synthesis, lipolysis) and its major function is to stimulate the elongation of bones in immature individuals by the following biochemical process:
1. Hypothalamus releases GHRH (Growth Hormone Releasing Hormone)
2. GHRH stimulates the pituitary to secrete hGH
3. hGH is transported through the bloodstream to the liver and other tissues
4. Liver and tissues respond to hGH by synthesizing IGF‑1, an insulin‑like growth factor
5. IGF‑1 stimulates the cells at the growth centers of bones leading to linear growth