Age-related bone loss and senile osteoporosis: evidence for both secondary hyperparathyroidism and skeletal growth factor deficiency in the elderly.
Aging is characterized by a decrease in bone volume, implying that net bone resorption exceeds net bone formation. This age-related bone loss can be regarded as the main determinant of hip fracture risk in the elderly. In the concept of senile osteoporosis, a key role has been attributed to vitamin D deficiency. Lack of vitamin D activity may affect femoral strength through impaired mineralization as well as through a hyperparathyroidism-mediated increase in bone resorption. In addition to vitamin D-related mechanisms, recent evidence has indicated a decline in the skeletal content of anabolic growth factors--such as insulin-like growth factor-I (IGF-I)--in femoral (cortical) bone, suggesting that skeletal growth factor deficiency may contribute to the age-related bone loss in the proximal femur as well. It is tempting to speculate that skeletal IGF-I loss might, at least partially, be accounted for by growth hormone deficiency. However, critical evidence does not yet support the concept that the decreased activity of the growth hormone-IGF-I-axis alters bone remodeling, and the extent to which serum concentrations of growth factors are reflective of skeletal activity remains to be clarified.
Boonen
S
S
Department of Internal Medicine, University Hospitals Leuven, Belgium.
Aerssens
J
J
Broos
P
P
Pelemans
W
W
Dequeker
J
J
D000368:Aged; D000375:Aging / Q000502:physiology*; D001846:Bone Development; D016723:Bone Remodeling; D001842:Bone and Bones / Q000378:metabolism; D006133:Growth Substances / Q000172:deficiency*; D006801:Humans; D006961:Hyperparathyroidism / Q000209:etiology*; D010024:Osteoporosis / Q000150:complications*
D006133:Growth Substances