The relationship of endogenous estrogen to bone density and bone area in normal postmenopausal women.

The relationship of endogenous concentrations of estrogen, in particular estrone, to the dominant radial bone density and bone area was examined in 78 normal postmenopausal women (mean age 57 years). The women were a subset of a population participating in a clinical trial designed to determine the effects of walking on bone loss. The data reported here were collected at baseline prior to randomization. Radial cortical bone density and bone area were measured at 30 per cent of the distance between the wrist and the elbow in the dominant arm. Estrone levels obtained by extraction and column chromatography were measured by radioimmunoassay. Estrone concentrations were cross-sectionally related to both radial bone density (r = 0.39, p less than 0.001) and bone area (r = 0.39, p less than 0.001). This relationship was independent of age, number of years since onset of menopause, and degree of obesity. In multiple regression analysis, estrone levels accounted for 15 per cent of the variance in bone density and bone area in this population. These results suggest that measurement of estrone in normal postmenopausal women may assist in the identification of women who are at high risk for osteoporosis and, thus, possible candidates for estrogen replacement therapy.