Reduced bone mineral density in patients with adult onset growth hormone deficiency

We have demonstrated previously that adults with isolated GH deficiency of childhood onset have a reduced bone mineral density (BMD) of vertebral trabecular bone [quantitative computed tomography (QCT): median Z score -1.3, P < 0.01, n = 12] and of cortical bone in the forearm [single photon absorptiometry (SPA): median Z score -2.9, P = 0.001, n = 7]. We have now examined BMD in 26 patients (13 men, 13 women), aged between 23.6 and 59.5 (mean 42.4) yr, with adult onset GH deficiency, defined as a GH response of less than 5 micrograms/L to provocative testing, of at least two years duration. BMD was measured using QCT for vertebral trabecular bone, dual energy x-ray absorptiometry (DXA) in the lumbar spine and femoral neck, and SPA in the forearm. There was a highly significant reduction in QCT (median Z score -1.07, P < 0.00005), in DXA of the lumbar spine (median Z score -0.76, P = 0.0001) and in SPA of the forearm (median Z score -0.86, P = 0.0001) but not in DXA of the femoral neck (median Z score -0.38, P = 0.35). There were no significant differences in Z scores between those patients with isolated GH deficiency and those with GH and gonadotrophin deficiency. There was a significant positive correlation between age at which BMD was measured and Z score (the older the patient, the higher the Z score) for QCT (r = 0.38, P < 0.05) and SPA (r = 0.48, P < 0.01) with a trend to a positive correlation for DXA of the lumbar spine and femoral neck. Patients were grouped according to estimated duration of GH deficiency (less than 5 yr, n = 7; 5-10 yr, n = 10; greater than 10 yr, n = 9). These groups did not show a significant difference in BMD at any site. We conclude that patients with adult onset GH deficiency (isolated or in conjunction with other pituitary hormone deficiencies) have a reduced BMD. Age at development of GH deficiency may be more important than duration of GH deficiency in determining the degree of reduction in bone mass. The impact of GH treatment on BMD in adults with adult onset GH deficiency requires investigation.