Variation in risk indicators of cardiovascular disease during the menstrual cycle: an investigation of within-subject variations in glutathione peroxidase, haemostatic variables, lipids and lipoproteins in healthy young women.
Variations in erythrocyte glutathione peroxidase activity, serum concentrations of lipids and lipoproteins and in blood coagulation and fibrinolysis during the menstrual cycle were studied in healthy young women. Blood samples were drawn twice a week for 9 weeks. A group of males was used for estimation of the influence on the results of factors which were not related to the menstrual cycle. Variations during the menstrual cycle were demonstrated in several of the factors analysed. The activity of glutathione peroxidase was lowest at ovulation. The clotting activity of factor II+ VII+X and the concentration of fibrinogen were lowest during mid-cycle, and the number of platelets increased in the follicular phase (days 5-9). Statistically significant variations in the fibrinolytic factors analysed (tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI) were not observed during the menstrual cycle. The serum concentrations of cholesterol and LDL cholesterol were significantly higher at the start of the menstrual cycle (days 3-8) than later in the cycle (days 19-24). The concentration of HDL cholesterol was lowest in the late luteal phase (days 23-28).