Question

What is the relationship between growth hormone and insulin-like growth factor in the growth of bones.

Answer 1

In short, IGF-1 acts as the principal mediator of growth hormone's anabolic effects.

Whilst growth hormone (GH) is capable of acting directly upon receptors at its target tissues, its downstream effects, like muscle and bone growth, are principally the result of indirect action through IGF-1. GH induces the synthesis and secretion of IGF-1 in the liver. Once circulating in the blood, IGF-1 acts at the peripheral tissues, e.g. muscle, cartilage, bone, etc.

One might say that IGF-1 mediates the effects of GH; in fact, IGF-1 has another name which succinctly describes its relationship with GH: somatomedin C. In a similar vein, GH is sometimes termed somatropin. In both cases, note the 'soma-' prefix, derived from the Greek for 'body'.