Treatment of post-menopausal osteoporosis with a combination of growth hormone and pamidronate: a placebo controlled trial.

OBJECTIVE

It is known that growth hormone can induce accelerated bone turnover in GH deficient people as well as healthy elderly people. In this study we examined the effect of recombinant human GH (rhGH) on bone mineral mass and bone turnover in the presence of the bone resorption inhibiting agent, pamidronate. Effects on body composition were also studied.

METHODS

Twenty-one post-menopausal osteoporotic women were treated with the bisphosphonate pamidronate during 12 months. During the initial 6 months rhGH (0.0675 IU/kg, 3 times/week) was administered in a placebo controlled fashion (10 vs 11 patients).

MEASUREMENTS

Bone mineral content (BMC) of the lumbar spine and femoral neck was measured with dual-energy X-ray absorptiometry and BMC of the distal and proximal forearm with single-photon absorptiometry. Body composition was measured with bioelectrical impedance and total body dual-energy X-ray absorptiometry. Serum IGF-I and biochemical indices of bone turnover were also measured.

RESULTS

The group treated with rhGH showed a two to three-fold increase in serum IGF-I levels. No effects on bone mineral mass were observed in the group treated with rhGH, either after the initial 6 months of treatment with rhGH or after the total period of 12 months. In women treated with pamidronate, however, a consistent increase of about 5% at the lumbar spine and somewhat less in the distal forearm was reached from 6 months onwards. In neither group was any change observed in BMC at the femoral neck or forearm. Compared to baseline, the biochemical measurements of bone turnover showed a decrease of about 50% in the pamidronate treated group, but this effect was blunted in the group additionally treated with rhGH. The body composition measurements showed clear effects of rhGH administration: a decrease in fat mass of about 5% and an increase in lean body mass of about 3%. However, these effects disappeared after the treatment with rhGH was stopped and both fat mass and lean body mass returned to initial values.

CONCLUSIONS

The present study suggests that treatment with rhGH blunted both the pamidronate induced accumulation of bone mineral mass and the reduction of biochemical markers of bone turnover. Furthermore, the positive effect of rhGH on body composition disappears completely after cessation of treatment with rhGH.