PLASMA HOMOCYSTEINE IN WOMEN ON ORAL ESTROGEN-CONTAINING CONTRACEPTIVES AND IN MEN WITH ESTROGEN-TREATED PROSTATIC-CARCINOMA

The mechanism by which oral oestrogen-containing contraceptives in women and oestrogen treatment of prostatic carcinoma in men increases the risk of vascular disease is unclear. These agents decrease serum concentrations of vitamin B-12, pyridoxal 5-phosphate, and folate, all of which are essential for the metabolism of the atherogenic amnio acid homocysteine. We found serum vitamin B-12 concentrations to be lower in 17 women using oral contraceptives (219+/-84 pmol l-1) than in 13 age-matched female controls (385+/-129, p<0.001), but similar values were obtained in the two groups both for fasting plasma homocysteine concentrations (9.1+/-2.4 vs 9.2+/-3.6-mu-mol l-1) and for the increase in these concentrations after methionine loading (19.2+/-7.5 vs 17.8+/-5.2-mu-mol l-1). In five men with prostatic carcinoma, high-dose oestrogen treatment decreased serum vitamin B-12 concentrations by a mean of 30% (p<0.05) within 4 weeks, during which fasting plasma homocysteine concentrations decreased (13.8+/-4.5 vs 10.5+/-2.8-mu-mol l-1) and response to methionine loading increased (12.4+/-3.4 vs 17.3+/-5.1-mu-mol l-1), though the latter changes were non-significant. Our findings do not support the hypothesis that hyperhomocysteinemia explains cardiovascular risk in women using oral oestrogen-containing contraceptives, or in oestrogen-treated men with prostatic carcinoma.