A possible role of estrone produced in adipose tissues in modulating postmenopausal bone density

Estrogen deficiency in postmenopausal women is a major contributing factor to bone loss occurring after menopause. Although serum estradiol levels decrease conspicuously, a considerable amount of estrone still exists in women after natural menopause. Since most of the estrone is converted from androgens in adipose tissues, we attempted to seek interrelationship among serum estrone levels, fat mass and bone mineral density (BMD) in postmenopausal women. Thirty women who underwent natural menopause at the age between 45 and 53 were examined for BMD of head, arms, trunk and legs, as well as total body fat and total lean body mass using a Lunar DPX, a dual energy X-ray absorptiometer. Serum estrone concentration in each subject was measured by RIA. BMD of all sites of bones examined showed a positive correlation with relative fat mass (total body fat/body weight). Serum estrone levels were positively correlated with BMD of arms, trunk and legs, as well as relative fat mass. Multiple regression analysis further demonstrated that relative fat mass and serum estrone levels were significantly related to BMD of both arms and trunk, and BMD of trunk, respectively. These results suggest that estrone produced in adipose tissues may have, if only in part, a role in modulating the loss of bone mass occurring after menopause.