From the Guidelines
Women exhibit a hypercoagulable state compared to men, with higher levels of coagulation factors, particularly during pregnancy and the luteal phase of their menstrual cycle, which increases their thrombotic risk. This difference is attributed to the influence of sex hormones, with estrogen promoting coagulation and testosterone having anticoagulant effects 1. The study by Sharma et al, as mentioned in the systematic review 1, found a trend of increasing hypercoagulability with increasing body mass index (BMI) in women.
Key differences in coagulation between females and males
- Women have higher levels of coagulation factors, such as factor VII, VIII, and von Willebrand factor, leading to enhanced clotting potential compared to men
- Cyclical variations in coagulation parameters occur throughout the menstrual cycle, with increased clotting tendency during the luteal phase when estrogen levels are higher
- Pregnancy further enhances the hypercoagulable state, with coagulation factors increasing by 20-200% to prevent excessive bleeding during delivery
- Men typically have higher levels of natural anticoagulants like antithrombin and protein C
Clinical implications
- Sex-based differences have implications for dosing anticoagulants, as women may require different dosages than men for optimal therapeutic effect
- Understanding these distinctions is essential for properly assessing thrombotic risk and tailoring anticoagulation strategies based on sex
- The use of viscoelastic testing, such as TEG, can help monitor hemostatic changes in obstetric patients with enhanced risk for thrombosis, as shown in the study by Tiscia et al 1
From the Research
Coagulation Differences between Females and Males
- Studies have shown that there are differences in coagulation between females and males, which can be attributed to various factors such as hormonal influences and genetic differences 2, 3, 4, 5.
- A study on mice found that females had higher mean A10 and A20 and median MCF values, indicating greater clot firmness in female versus male mice 4.
- In humans, a study found significant and consistent differences in coagulation and fibrinolytic laboratory parameters among healthy women of reproductive age from different ethnic groups and geographical locations 5.
- Hormonal contraceptives have been shown to affect coagulation in females, with changes in the level of inhibitors of the coagulation system and increased alpha 1-antitrypsin levels, which may be a biochemical risk factor for thromboembolic disorders 2.
- Sex differences in cardiovascular diseases, including those related to coagulation, have been attributed to the combined expression of genetic and hormonal differences between women and men 3.
Factors Influencing Coagulation Differences
- Haematocrit has been found to affect INR differences between whole blood point-of-care coagulation monitors and reference prothrombin time in plasma, with a negative correlation between haematocrit and INR difference 6.
- Hormonal status and pregnancy history are important considerations in the diagnosis and treatment of cardiovascular diseases, including those related to coagulation, in women 3.
- Genetic differences between males and females may also contribute to differences in coagulation, although further research is needed to fully understand the underlying mechanisms 4.