Influence of menstrual cycle phase on serum concentrations of alpha 1-acid glycoprotein.

Serum concentrations of alpha 1-acid glycoprotein (AAG) were studied in nine healthy women at four times in their menstrual cycles. AAG concentrations were significantly higher on day 4 than on days 12, 20, and 28 (with the first day of menstrual flow considered to be day 1). The mean AAG concentration (mg dl-1) on day 4 was 78.55 +/- 5.03 (mean +/- s.e. mean), 70.19 +/- 4.80 on day 12, 70.63 +/- 6.67 on day 20, and 70.40 +/- 5.97 on day 28. Although these results should be considered preliminary because of the small sample size, we conclude that physiologic changes over the course of the menstrual cycle may affect serum AAG concentrations. Since AAG is a major binding protein for several important drugs, the potential exists for altered drug binding and drug effects, and further study of individual drugs is justified.