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

Summary 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 −0.009g/cm2, P=0.01), forearm Integral BMD (SPA: median change −0.016g/cm2, P=0.03), lumbar spine BMD (DXA: median change −0.022g/cm2; P=0.003) and femoral neck BMD (DXA: median change −0.029g/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.