Related Experiment Videos
Risks and mechanisms of cardiovascular events in users of oral contraceptives
1MRC Epidemiology and Medical Care Unit, Northwick Park Hospital, Harrow, Middlesex, United Kingdom.
Insights
Oral contraceptives increase the risk of blood clots, with higher doses of estrogen and progestogen posing greater dangers. These risks are linked to changes in blood clotting factors and blood pressure.
Area of Science:
- Cardiovascular Science
- Pharmacology
- Thrombosis Research
Background:
- Large British studies investigated the vascular effects of oral contraceptives (OCs).
- Previous research linked oral contraceptive use to thromboembolic episodes.
- Established knowledge on clotting factors and cardiovascular risk in men.
Purpose of the Study:
- To analyze the dose-dependent relationship between estrogen and progestogenic components of OCs and vascular risks.
- To explore the potential mechanisms linking OC use to thromboembolism and arterial disease.
Main Methods:
- Analysis of data from three large British studies on oral contraceptive use.
- Review of established associations between clotting factors (Factor VII, VIIC, fibrinogen) and ischemic heart disease in men.
- Correlation of estrogen and progestogen doses with observed vascular events.
Main Results:
- Risk of venous and arterial thromboembolism increases with higher estrogen doses in OCs.
- Progestogenic component of OCs shows a dose-dependent link to arterial disease risk, but not venous events.
- Estrogen dose-dependently affects clotting factors VIIC and fibrinogen, suggesting a role in OC-related thromboembolism.
Conclusions:
- The risk of thromboembolism associated with oral contraceptives is substantially mediated by increased blood coagulability.
- The link between progestogens in OCs and arterial disease risk may involve effects on blood pressure.
Abstract:
Three large British studies on the vascular effects of oral contraceptives have established that the risk of thromboembolic episodes, both venous and arterial, rises with increasing estrogen dose. Two of these studies have also demonstrated a dose-dependent relationship between the progestogenic component of oral contraceptives and the risk of arterial disease, though not of venous events. In men, high levels of factor VII coagulant activity, VIIC, and plasma fibrinogen are associated with an increased risk for ischemic heart disease. In view of the dose-dependent relationship between estrogen and these two clotting factors, especially VIIC, it is likely that the effects of oral contraceptive usage on the risk for thromboembolism are mediated substantially through the level of coagulability. The relationship between the progestogenic component of oral contraceptives and the risk for arterial disease is probably related, at least in part, to the effects of progestogens on blood pressure.