[Estrogens and bone metabolism].
The authors present a review referring to cellular and biochemical control systems of bone remodeling as well as the effect of estrogens on modulation of bone metabolism. Systemic and local control factors such as PTH, calcitonin, vitamin D, prostaglandins, insulin-like growth factor-1, transforming growth factor-beta are analyzed as possible indirect targets for the estrogen induced inhibition of bone resorption. A direct receptor-linked action of estrogens on the osteoblast-lining cell unit, the most important modulator or bone metabolism, is furtherwise examined. The precise mechanism of the beneficial effect of estrogens for the prevention of postmenopausal bone loss and the treatment of established osteoporosis has not yet been clearly identified, but it seems likely that multiple mechanisms may be involved since postmenopausal osteoporosis itself appears as a heterogenic clinical condition related to multiple pathogenetic factors.