The role of serum concentrations of sex steroids and bone turnover in the development and occurrence of postmenopausal osteoporosis.

It has been debated whether postmenopausal osteoporosis is characterized by high or low bone turnover and whether circulating levels of sex steroids contribute to the occurrence of osteoporotic fractures. We examined 154 70-year-old women with or without osteoporotic fractures, and 178 early postmenopausal women with a "rapid" or a "slow" bone loss. In all participants, we determined markers of bone formation (serum alkaline phosphatase (AP) and serum bone Gla protein (BGP)), markers of bone resorption (fasting urinary calcium/creatinine (FU Ca/Cr) and hydroxyproline/creatinine (FU Hpr/Cr)), and serum estrone (E1), estradiol (E2), androstenedione (A), and fat mass. The 70-year-old women with osteoporotic fractures had significantly elevated AP (P less than 0.001), BGP (P less than 0.001), and FU Hpr/Cr (P less than 0.001) compared with the group without fractures. In the group of early postmenopausal women, the "rapid" bone losers had significantly increased FU Hpr/Cr (P less than 0.001) and FU Ca/Cr (P less than 0.001). E1, E2, A, and the fat mass did not differ in the groups with and without osteoporotic fractures, whereas the "rapid" bone losers had significantly lower E1 (P less than 0.05), E2 (P less than 0.05), and fat mass (P less than 0.01) than the "slow" bone losers. It is concluded that patients with manifest osteoporosis and early postmenopausal women with a rapid bone loss have increased biochemical markers of bone turnover. Moreover, the present study demonstrates that early postmenopausal women with an "excessive" bone loss have significantly decreased serum estrogens, whereas it is not possible to detect low estrogens in women with osteoporotic fractures.