Effect of menopause and hormone replacement therapy on urinary excretion of pyridinium cross-links: a longitudinal and cross-sectional study.

OBJECTIVE: To study longitudinally the effect of the menopause and hormone replacement therapy on the new markers of bone resorption: urinary excretion of pyridinoline and deoxypyridinoline. DESIGN AND PATIENTS: Urinary pyridinoline and deoxypyridinoline were measured every 3 months for 2-3 years in 15 healthy women aged 45-54 years. Nine remained premenopausal and six became post-menopausal during the study. Urinary pyridinoline and deoxypyridinoline were also measured before and after 3 months of either placebo or hormone replacement therapy in 65 post-menopausal women, aged 45-54 years, who were participating in a double-blind study. MEASUREMENTS: Urinary pyridinoline and deoxypyridinoline were measured in fasting urine samples by spectrofluorometry after high performance liquid chromatography and corrected for creatinine excretion. RESULTS: Urinary pyridinoline and deoxypyridinoline remained almost constant during the premenopausal period. Both started to increase 6 months after the last menstrual bleeding and the mean post-menopausal values were 30-50% higher than the premenopausal values in the same subjects (values in nmol/mmol creatinine given as mean +/- SEM: urinary pyridinoline (premenopausal) = 29 +/- 2 vs urinary pyridinoline (post-menopausal) = 38 +/- 6, P < 0.05; urinary deoxypyridinoline (premenopausal) = 8 +/- 1 vs urinary deoxypyridinoline (post-menopausal) = 12 +/- 1, P < 0.05). Three months of post-menopausal hormone replacement therapy decreased (P < 0.001) both to premenopausal levels. CONCLUSION: Urinary pyridinoline and deoxypyridinoline, new markers of bone resorption, remain fairly constant in the years before the menopause and start to increase about 6 months after the last menstrual bleeding. This increase is reversed by hormone replacement therapy.