Changes in bone resorption during the menstrual cycle

To determine if the cyclic changes of female sex hormones during the menstr ual cycle are related to changes in bone formation and resorption, we measu red serum bone-specific alkaline phosphatase (BAP) and osteocalcin (OC) and bone resorption markers, serum and urine deoxypyridinoline (Dpyr), three t imes per week during one menstrual cycle in 20 healthy premenopausal women. Serum estradiol (E-2) and progesterone (P) showed characteristic cyclic fl uctuations. Serum Dpyr was higher during the follicular phase (FP) than in the luteal phase (p = 0.027), Serum BAP, OC, and urine Dpyr levels did not change substantially across the cycle. Serum Dpyr correlated negatively wit h serum E-2 values measured 6 (p = 0.011) and 8 (p = 0.001) days earlier an d with P measured concurrently (p = 0.033) 2 (p = 0.002), 4 (p = 0.003), an d 6 (p = 0.014) days earlier. BAP correlated negatively with E-2 measured 6 days earlier (p = 0.006). We found no statistically significant correlatio ns of E-2 or P with OC or urine Dpyr within women over their cycles, BAP wa s positively correlated with concurrent serum Dpyr (p = 0.015) during the m enstrual cycle, Serum OC levels correlated inversely with age (r(s) = -0.48 , p = 0.036). Women with higher mean urine Dpyr levels had higher mean seru m OC levels (r(s) = 0.49, p = 0.033) and showed a trend toward lower hip bo ne mineral density (r(s) = -0.40, p = 0.078). We conclude that the low leve l of E-2 and/or P observed during the FP of the normal menstrual cycle is a ssociated with increased bone resorption. These relationships suggest that normal women experience monthly episodes of increased bone resorption from menarche to menopause.