Background

Although it is well known that bone mineral density (BMD) loss occurs after menopausal transition, there are only few previous studies that describe differences of BMD and biochemical bone markers in women of pre- and postmenopausal periods. The purpose of this study was to find factors that contribute to loss of BMD after menopause and to show changes of BMD and biochemical bone markers during pre- and postmenopausal periods by retrospective cohort study.

Methods
This retrospective cohort study was performed from Jan. 1995 to Jan. 2001 at a health promotion center. Twenty one healthy perimenopausal women were enrolled. BMD and biochemical bone markers were checked more than two times during the study period. Changes of BMD and biochemical bone markers between pre- and postmenopausal state were compared by paired t-test. Pearson correlation and multiple regression were performed to find the contributing factors to loss of BMD after menopause.

Results
Postmenopausal BMD (164.65±36.34 mg/cm³) was significantly decreased to 16.49±16.91 mg/cm³ (P＜0.001) as compared with premenopausal BMD (181.14±40.81 mg/cm³). In biochemical bone markers only urine deoxypyridinoline had a significant difference (3.30±3.97 nMDP/mMcre, P＜0.05) Only premenopausal BMD contributed to decreasing rate of BMD between the two states and the loss of BMD after menopause (P＜0.05).

Conclusion
In perimenopausal healthy women, postmenopausal BMD was significantly decreased as compared with premenopausal BMD. And only premenopausal BMD was shown to be a contributing factor to decreasing rate of BMD between the two states and the loss of BMD after menopause. It suggests that premenopausal BMD is important in predicting postmenopausal osteoporosis and efforts to prevent loss of BMD before menopause can prevent progress of postmenopausal osteoporosis.