Effect of growth hormone replacement on bone mass in adults with adult onset growth hormone deficiency.

OBJECTIVE: Previous studies of the effect of GH replacement on bone mass in adults with GH deficiency have produced conflicting results. We have studied the effect of 6 and 12 months of GH replacement on bone mass in adults with adult onset GH deficiency.

DESIGN: Double blind placebo controlled study of GH replacement (0.125 IU/kg/week for the first month and 0.25 IU/kg/week thereafter) for 6 months and an open study for a further 6 or 12 months.

PATIENTS: Twenty-two adults (10 men, 12 women), aged 41.5 +/- 2.1 years (mean +/- SE, range 23.6-59.5), with adult onset GH deficiency.

MEASUREMENTS: Single-energy quantitative computed tomography was used to measure vertebral trabecular bone mineral density (BMD), single-photon absorptiometry (SPA) was used to measure forearm cortical and integral bone mineral content and BMD and dual-energy X-ray absorptiometry (DXA) was used to measure lumbar spine, femoral neck, trochanteric and Ward's triangle integral BMD.

RESULTS: After 6 months of GH replacement (n = 21) there was a significant decrease in forearm cortical BMD (SPA: median change -0.009 g/cm2, P = 0.01), forearm integral BMD (SPA: median change -0.016 g/cm2, P = 0.03), lumbar spine BMD (DXA: median change -0.22 g/cm2; P = 0.003) and femoral neck BMD (DXA: median change -0.029 g/cm2, P = 0.006). After 12 months of GH replacement (n = 13) there was a significant decrease in lumbar spine BMD (DXA: median change -0.035 g/cm2, P = 0.002) from baseline. There was no significant increase in bone mass at any site after 6 or 12 months of GH replacement. Change in bone mass was not influenced by sex of the patient or by presence or absence of additional pituitary hormone deficiencies.

CONCLUSION: The response of bone mass to 6 and 12 months of GH replacement in adults with adult onset GH deficiency is disappointing. Longer-term studies are required to determine whether prolonged GH replacement has a beneficial effect on bone mass.