Clinical review 61: Effects of growth hormone on human bone biology.

GH has considerable importance in the normal development and growth of bone. An additional role in the maintenance of the adult skeleton is suggested by the alterations in bone mineral density observed in states of deficient or excess GH secretion and in the bone formation response to GH replacement in GHD patients. Deficiency in the secretion of GH is also observed, with increasing and striking frequency after middle-age despite the lack of any defined pituitary disease or injury. Although a causal relationship between hyposomatotropism and osteopenia in normal elderly patients is hypothetical, intriguing therapeutic questions are raised. Preliminary trials of hGH in osteoporosis have not resulted in increases in BMD, but such studies suffer from methodological limitations, chief of which is the failure to account for the GH/IGF-I status of their subjects. Osteopenic patients with the lowest IGF-I levels may need to be assessed independently. The utility of hGH may be in preventing the senile component of osteoporosis, which appears to result mainly from defective bone formation. Such studies will require appropriate patient selection, longer treatment periods, and more sensitive measures of bone density. Combination and/or coherence therapy with other agents, particularly those that attenuate bone resorption, may also prove useful.