Concentration of cytosolic estrogen receptors in patients with postmenopausal osteoporosis

Abstract

Although all postmenopausal women are relatively estrogen-deficient, osteoporosis develops in only some of them. This could be related to a greater-than-normal degree of postmenopausal failure in sex hormone production or to a decrease in biologic effect at target tissue sites. We compared the concentration of sex steroids in serum and the concentration of cytosolic estrogen receptors in one target tissue (obtained by biopsy of the uterine cervix) in 18 women with postmenopausal osteoporosis and in 18 age-matched postmenopausal control subjects. Serum androstenedione and estrone were not significantly lower and serum estradiol was only marginally lower in the osteoporotic patients. Estrogen-receptor concentration in cervical tissue from both postmenopausal groups was not significantly different. We concluded that abnormalities of residual postmenopausal production of sex steroids and binding of sex steroids to cervical target tissue are not the major factors accounting for the decreased bone mass in women with postmenopausal osteoporosis.

PIP: Osteoporosis occurs in some postmenopausal women in spite of their estrogen-deficient status, possibly because of variations in postmenopausal production of sex steroids, or of differences in responsiveness of target tissue to low postmenopausal concentrations of sex steroids. These possibilities were investigated by measuring sex steroids in serum and specific cytosolic estrogen receptors in 18 postmenopausal osteoporotic women (mean age, 63.8 years) and a control group of 18 postmenopausal women (mean age, 65.9) undergoing hysterectomies for nonmalignant diseases. Estrogen binding was measured by the charcoal absorption technique. Results of the assay were expressed by a Scatchard plot of bound/unbound estradiol and bound labeled hormone. Serum androstenedione and estrone were not significantly lower in the osteoporotic patients; serum estradiol was also only marginally lower in the osteoporotic patients. Both groups did not exhibit any significantly different estrogen-receptor levels in cervical tissues. The findings suggest that abnormalities of residual postmenopausal production of sex steroids and binding of sex steroids to cervical target tissue are not responsible for postmenopausal osteoporosis in some women.