An integrated view of the role of the endocrine system in the genesis of the osteoporosis associated with aging.

Estrogen deficiency is the major determinant of increased bone resorption and bone loss occurring in early menopause (first 5-6 years). The increased bone resorption is probably caused by the release of immune system cytokines such as IL-1, IL-6 and TNF by osteoblasts, the biosynthesis of which is no longer suppressed by estrogen. PTH secretion, although decreased in early menopause, may also contribute to increased bone destruction because of the presence of cytokines such as IL-1 and TNF which increase the sensitivity of bone to the resorptive effects of PTH. For the same reasons, the bone-destructive effects of increased serum levels of PTH occurring in the late menopause may be exaggerated.