Effect of oral contraceptive steroids on vitamin A status of women and female rats.

Abstract

The interaction between oral contraception and vitamin A in women of low income women is the study interest. 1 study in a small group of women has been completed and the other more comprehensive investigation -- sponsored by the Human Reproduction Unit of the World Health Organization (WHO) -- is now in progress. The 1st study included 2 parts. A cross-sectional investigation was conducted. Women who had been using OC for 6-12 months were compared with a matched group of women who had never taken OC and a partial follow-up study in which a women was examined initially and then at 1 or more points of time in the first 6 months. Each woman served as her own control. The women took either Ovral or Ovulen-50. In the WHO study 3 types of hormonal contraceptives are being tested for their metabolic side effects: 1) 0.05 mg ethinyl estradiol and 0.15 mg d-norgestrel oral pill; 2) 0.03 ethinyl estradiol and 0.15 mg d-norgestrel oral pill; and 3) medroxyprogesterone acetate (DMPA) 150 mg once in 3 months injection. The 2 oral pills are coded as LNA and LNB trade preparations and it is not known which is the 50 mg estrogen pill and which is the 30 mg estrogen pill. The hope is to examine 60 women/preparation initially and at the end of 1 year. The investigation on DMPA has been discontinued because of a ban on the drug. Vitamin A was estimated in cyclohexane extracts of the plasma by ultra violet spectrophotometry before and after irradiation with ultra-violet light. Both Ovulen-50 and Ovral elicited a rise in plasma vitamin A. The extent of increase was greater with Ovulen-50 suggesting that the progestagen component of this OC modifies the response. The 1st cycle examination in the case of the LNA and LNB pill preparations was performed only 10-15 days after starting the contraceptive and within that interval plasma vitamin A levels were raised. The magnitude of the change in plasma vitamin A was similar with LNA and LNB. The important questions arising from these results are: 1) what is the biochemical basis for the observed change in plasma vitamin A; and 2) what is the clinical significance of this change. 3 explanations supported by limited experimental data have been put forth to explain the rise in plasma vitamin A levels associated with OC use: 1) rise in plasma vitamin A is due to a general lipemia which is often seen in women using OC; 2) OC enhances the conversion of carotene to retinol; 3) the rise in plasma vitamin A in OC users is probably secondary to an increase in retinol-biding protein (RBP).