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

Summary

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 womenwith osteoporotic fractures had significantly elevated AP (P<0.001), BGP (P<0.001), and FU Hpr/Cr (P<0.001) compared with the groupwithout fractures. In the group of early postmenopausal women, the “rapid” bone losers had significantly increased FU Hpr/Cr (P<0.001) and FU Ca/Cr (P<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<0.05), E₂ (P<0.05), and fat mass (P<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.