Low Bone Mass Is an Infrequent Feature of the Adult Growth Hormone Deficiency Syndrome in Middle-Age Adults and the Elderly

Abstract

Low bone mass is considered a characteristic feature of adult GH deficiency (GHD). Although low bone mass is universally observed in cohorts of GHD adults of young age, the situation is less clear with regard to cohorts of GHD middle-age adults or the elderly. We have examined the relationship between bone mineral density (BMD) and age in 125 severely GHD adults using dual-energy x-ray absorptiometry. This relationship was further examined with a calculated measure of volumetric BMD, bone mineral apparent density (BMAD). A significant positive correlation was observed between age and BMD (Z scores) at the lumbar spine (r = 0.39, P < 0.0001), femoral neck (r = 0.47, P < 0.0001), total hip (r = 0.47, P < 0.0001), and ultradistal (r = 0.46, P < 0.0001) and distal radius (r = 0.52, P < 0.0001). Young adults were observed to have reduced bone mass, whereas the elderly GHD patients had normal Z scores. After division of the cohort into age ranges (<30, 30-45, 45-60, and >60 yr), BMD Z scores at all five skeletal sites increased significantly across the age groups from youngest to oldest (P < 0.001). When BMD was assessed using absolute values (g/cm(2)), in contrast to the decline in BMD observed with aging in a normal population, BMD at the total hip and ultradistal and distal radius increased across the age strata of GHD adults (P = 0.003, P = 0.004, and P = 0.002, respectively), and a trend toward an increase in lumbar spine and femoral neck BMD was also observed. No significant change in BMAD was observed across the four age groups. The percentage of patients observed to have BMD Z scores of less than -2.0 at the lumbar spine was 30, 11, 11, and 14% in the four age groups, respectively. At the femoral neck, the corresponding percentages were 36, 6, 7, and 0%, respectively. In summary, we have shown that the effect of severe GHD on BMD is dependent on age. Low bone mass was observed in the young patients; however, patients over the age of 60 yr demonstrated a mean BMD Z score above that of the reference population and significantly greater BMD (g/cm(2)) when compared with young GHD adults. Few patients were observed to have BMD Z scores below -2.0 except patients aged less than 30 yr, which, in part, was explained by their shorter stature. Thus, significantly reduced bone mass is not a frequent observation in adults with GHD.