Endocrine Abstracts

Limited data exist describing direct volumetric measures of BMD (g/cm³) in adults with severe GHD or GH-insufficiency. We measured BMD in 30 GHD adults (peak GH to stimulation <3 mcg/l), 24 GH-insufficient adults (GHI, pGH 3 - 7 mcg/l), and 30 age/gender matched control subjects by DXA and pQCT.

DXA performed at the lumbar spine, femoral neck, and total hip confirmed GHD adults to have reduced BMD (g/cm²) at all sites (p = 0.05, p = 0.05, & p = 0.007). Patients with GHI showed intermediate BMD (g/cm²) at the lumbar spine and total hip compared with severely GHD and control subjects. BMD at the total hip demonstrated a trend towards reduced BMD in GHI adults compared with healthy adults (p = 0.066), but no significant difference to GHD adults. Volumetric BMD (mg/cm³) was measured using pQCT from slices at a distance of 4% and 50% of the forearm length from the wrist. Neither cortical or trabecular BMD was significantly different between the study groups at the 4% site. At the 50% site cortical density was not significantly different between the three study groups. Biomeasures of bone strength were calculated from the relative density and distribution of bone mineral at the 50% site. The moment of resistance (p = 0.05), axial area moment of inertia (p = 0.06), and polar stress-strain index (SSI polar, p = 0.05) were lower in the GHD adults compared with the healthy controls. These biomeasures in the GHI adults were intermediate to the GHD and healthy control subjects.

Although GHD and GHI adults were found to have low bone mass by DXA, volumetric BMD measured by pQCT was not significantly different between the three study groups. It is likely therefore that much of the low bone mass in GHD adults relates to differences in height and consequently bone thickness.