Changes of plasma total homocysteine levels during the menstrual cycle

It is known that plasma total homocysteine (tHcy) levels are lower in premenopausal and pregnant women compared with postmenopausal women. To confirm the suggestion that sex steroid hormones are nongenetic factors affecting homocysteine metabolism, we investigated the effect of natural steroid hormone levels on the fasting plasma tHcy in healthy women during the menstrual cycle.

Fifteen premenopausal women were enrolled in this study. Plasma tHcy, estradiol, progesterone and cortisol concentrations were measured in the luteal and follicular phase. The plasma tHcy concentration was determined by high performance liquid chromatography with fluorescence detection, and the steroid hormones by RIA methods.

Mean homocysteine values increased from 7.8 micromol L-1 in the luteal phase to 8.9 micromol L-1 in the follicular phase (P < 0.000005, Student's paired t-test). We also found slight negative but insignificant correlations of homocysteine levels with estradiol in both phases of the menstrual cycle. In the case of cortisol and progesterone, no significant correlations with plasma homocysteine were found.

The study provides the first evidence of significant differences in plasma homocysteine concentration during the menstrual cycle. From our observed findings it is necessary to account for the phase of the menstrual cycle when determining homocysteine in premenopausal women.