Urinary biochemical markers for bone resorption during the menstrual cycle.

In order to analyze the effects of serum ovarian steroid hormones on bone metabolism during the menstrual cycle, we have measured urinary levels of type I collagen cross-linked N-telopeptide (NTx), hydroxylysylpyridinoline (HP), lysylpyridinoline (LP). and hydroxyproline (OH-Pr) in nine healthy Japanese women, aged 22-43 years, with normal ovarian function. The cycles were synchronized by serum LH peaks, and follicular and luteal periods were normalized by lengths. Serum gonadotropins and ovarian sex steroids showed significantly different cyclic variations during the menstrual periods. Urinary NTx remained unchanged during the early follicular period, showed a rise during the mid- and late follicular period, and a fall during the mid- and late luteal periods. There were significant differences in NTx levels between early follicular period and midfollicular period (P < 0.01), or late follicular period (P < 0.05), and between early luteal period and late luteal period (P < 0.05). The levels of HP and LP showed a rise during the early an midfollicular periods and a fall during the midluteal period. The correlation of NTx with urinary OH-Pr was better than with urinary HP or LP (r = 0.731 versus r = 0.449 or r = 0.634). This variation suggests that cyclic changes in serum ovarian sex steroids might modulate bone resorption markers during the menstrual cycle.