Growth hormone and bone.

The significance of growth hormone in the psychology of bone remodeling is now strongly recognized. It influences osteoblast function and growth in vitro as well as in vivo. Although in vivo bone resorption is also stimulated, short administration of growth hormone induces a sustained stimulation of osteoblastic function, whereas the influence on resorption probably diminishes earlier. Growth hormone concentrations in plasma decline with age. Growth hormone and growth hormone response to growth hormone releasing factor are influenced by sex hormones, thereby changing around the menopause. In several aspects features of aging resemble those of a state of growth hormone deficiency. This holds true for body composition, the immune system as well as bone density. Therefore, it has been argued that declining growth hormone function, along with other factors, might be a causal factor in osteoporosis. Consequently, growth hormone substitution in the elderly might be applicable to maintain and possibly improve bone density and structure. The first clinical trials using recombinant growth hormone give hopeful results.