Decreased bone mineral density associated with early menopause progresses for at least ten years: cross-sectional comparisons between early and normal menopausal women.

To establish whether early onset of menopause carries an increased risk of osteoporosis, we compared the bone mineral density (BMD) of the second to fourth lumbar vertebrae (L2-4) between 18 women who had menopause before 43 years of age (early menopause group) and 19 women who had menopause after reaching 43 years of age (normal menopause group). Serum levels of calcium, phosphorus, calcitonin, intact parathyroid hormone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E2), and alkaline phosphatase activity were measured, and urine samples were analyzed to derive calcium/creatinine, hydroxyproline/creatinine, pyridinoline/creatinine, and deoxypyridinoline/creatinine (D-Pyr/Cr) ratios. Mean BMD was significantly lower in the early menopause group than in the normal menopause group, and individual BMD values in about half of the subjects in the former group were below the fracture threshold for Japanese women. Serum concentrations of LH, FSH, and E2 were slightly, but not significantly, lower in the early menopause group than in the normal menopause group. The D-Pyr/Cr ratio was significantly higher in the early menopause group than in the normal menopause group. There was no correlation between L2-4 BMD and age or the number of years after menopause in the normal menopause group, but both age and the number of years after menopause were negatively correlated with L2-4 BMD in the early menopause group. These results indicate that BMD in women who have early menopause continues to decline for up to 10 years, and that menopause and aging increase the risk of osteoporosis.