Lack of change in serum angiotensin-converting enzyme activity during the menstrual cycle

myocardial ischaemia, angiotensin- converting enzyme, oestrogen, renin-angiotensin system, genotype Abstract Introduction. The Deletion (D) rather than Insertion (I) variant of the angiotensin-converting enzyme (ACE) gene is associated with higher circulating ACE activity. Meanwhile, coronary risk rises with the menstrual nadir in oestrogen levels, exogenous oestrogen reduces serum ACE activity (with a greater reduction the higher the baseline ACE activity), and pharmacological reduction in ACE activity is cardioprotective. Alterations in coronary risk associated with the menstrual cycle may thus be mediated through (genotype-dependent) changes in ACE activity.We have examined this hypothesis. Materials and methods. Twenty-three healthy female subjects (12 II, 11 DD genotype) were studied. None were taking oral contraceptive agents. Blood was assayed for oestrogen, follicle stimulating hormone (FSH), luteinising hormone (LH), progesterone and ACE activity every three days throughout their menstrual cycle. Results ACE activity was unrelated to oestrogen, FSH or LH during the menstrual cycle, irrespective of ACE genotype. Conclusions. The increase in myocardial ischaemia during low oestrogen phases of the menstrual cycle does not appear mediated through a fall in serum ACE activity.