ROLE OF GROWTH-HORMONE AND SEX STEROIDS IN ACHIEVING AND MAINTAINING NORMAL BONE MASS

It is now established that adults with growth hormone (GH) deficiency, of childhood or adult onset, have reduced bone mass. GH deficiency is believed to interfere with acquisition of bone mass, although an alte rnative mechanism is required to explain the reduction in bone mass pr esent in adults who acquire GH deficiency after peak bone mass has bee n achieved, GH replacement increases bone turnover and may increase bo ne mass in the longer term, although short-term studies show a decreas e in bone mass which can be explained by an increase in bone resorptio n before new bone formation occurs. Abnormalities of GH secretion have also been implicated in the development of osteoporosis, but the effe ct of GH treatment on bone mass in such patients is disappointing. Sex steroids have an important role to play in the acquisition of bone ma ss, and reduced sex steroid levels during adolescence have a deleterio us effect on bone mass. The importance of sex steroids in the maintena nce of bone mass is illustrated by the development of osteopenia in me n and women with hypogonadism, and by the preservation of bone mass by restoration of normal endogenous sex steroid levels, or by treatment with exogenous sex steroid. Sex steroids also influence circulating le vels of GH and insulin-like growth factor-1, and the interaction betwe en these hormones is likely to be important in the acquisition and mai ntenance of normal bone mass.