Objective: We examined the effects of estrogen and progesterone on the plasma platelet-activating factor (PAF)-acetylhydrolase activity and lipoprotein concentrations in men.
Method: Ten healthy men received 6 days of oral mestranol (0.24 mg/day) followed by 6 days of oral norethisterone (20 mg/day). The PAF-acetylhydrolase activity and lipoprotein profiles were determined in each subject prior to and following mestranol loading and following norethisterone administration.
Result: The mestranol caused a significant decrease in both the plasma PAF-acetylhydrolase activity and the low-density lipoprotein (LDL) cholesterol concentrations of 26.4% and 26.9%, respectively; norethisterone appeared to revert the PAF-acetylhydrolase activity and LDL cholesterol concentrations to the levels observed prior to mestranol loading. In addition, the plasma PAF-acetylhydrolase activity was positive correlated with the LDL cholesterol concentration (r = 0.58, P < 0.001).
Conclusion: The results of this study indicate that mestranol and norethisterone exert an effect on the plasma PAF-acetylhydrolase activity in men, possibly by influencing plasma LDL cholesterol concentrations.