Growth hormone and bone metabolism.

GH is a potent anabolic hormone for bone and calcium metabolism, not only via direct effects but also mediated through other systems. The individual effects on bone metabolism are summarized in Table 1. Some of the signs (low BMD and low serum osteocalcin) and symptoms (increased prevalence of vertebral fractures) seen in patients with GHD may be due to the lack of GH itself, others may be due to secondary hormone deficiencies or changes in body composition induced by GHD. GH treatment can reverse changes of calcium metabolism. Whether it is able to increase bone mass still needs to be determined in larger and longer studies. Some patients with established osteoporosis and vertebral fractures seem to suffer from GHD. Treatment of osteoporosis with GH has not previously been successful, but studies with more patients over several years to investigate the effects of GH treatment on vertebral fracture rates are lacking. As GH seems to reverse some signs of old age, such as muscle weakness and reduced exercise capacity, it is possible to speculate that GH could prevent the occurrence of hip fractures in elderly people.