Why Does Estrogen Cause Blood Clots? What You Need To Know
The fact that blood clots is a good thing. It’s what allows us to think of minor, ordinary cuts, scrapes, and bruises as trivial rather than life-threatening.
However, blood clots become much more serious when they’re travelling around your insides, potentially blocking blood flow to your brain (stroke) or heart (heart attack), or when a deep venous thromboembolism (DVT) moves up from your legs to your lungs (pulmonary embolism).
According to the US Surgeon General, pulmonary embolism from DVTs cause at least 100,000 deaths each year. And because we become more likely to suffer a blood clot as we age, it’s important we understand what they are, why does estrogen cause blood clots, and what we need to do to minimize our risk.
Menopause and Perimenopause Blood Clots
The link between hormones, menopause and blood clots in women is complicated and not entirely understood. Understandably, many women are concerned about their risk of blood clots if they decide to take birth control or use HRT to manage perimenopause and menopause symptoms.
To get some answers, we turned to Dr. Emily Larmore Cooper, MD, of Sound Medicine and Wellness.*
How do blood clots in women form?
Dr. Emily: Blood clots form because the blood slows down or stops moving. Anything that prevents your blood from moving can make you more prone to developing a blood clot. Common examples include: genetic factors; personal history of a blood clot; immobility either from surgery, chronic illness or even travel; age, smoking, obesity and hormones all increase your risk of developing a blood clot.
Why Does Estrogen Cause Blood Clots?
Dr. Emily: The risk of developing a blood clot increases with age, particularly after the age of 40. Taking hormones also causes a small but increased risk of developing a blood clot. Together, the two combine to increase your risk. However, smoking alone increases your risk of a blood clot by 8.8 times.
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There is a dose-dependent risk and lower doses of estrogen carry less risk. The risk of developing a blood clot is increased in the first 6-12 months of starting hormones. Hormones and bloodclosts does not increase with the length of time that someone it. Your risk is eliminated when you stop the hormones. There does not appear to be an increased risk with progesterone-only formulations.
Are blood clots more likely in perimenopause or menopause?
Dr. Emily: Women are at highest risk of a blood clot with pregnancy and in the post-partum period. This is an even higher risk than women taking contraceptives.
“There is a small but significant increased risk of blood clot in
women taking hormone therapy,
but for healthy postmenopausal women,
the absolute risk is very low.”
In the Women's Health Initiative study, a 2-fold increase in blood clot was found in women taking HRT. The risk was highest within the first year of taking the hormone replacement. Age is an independent risk factor for blood clots. The risk may vary with the type/dose and route of estrogen, but at this time, there is insufficient evidence to recommend one type of hormone replacement over another. There is a small but significant increased risk of blood clot in women taking hormone therapy, but for healthy postmenopausal women the absolute risk is very low.
If I have a personal or family history of blood clots, does that mean no hormones, like HRT?
Dr. Emily: A family history of blood clot could indicate that you have an inherited risk toward blood clots. You should speak with your doctor about whether you should undergo genetic testing. If you have a genetic predisposition toward clotting, then you should have a discussion with your physician about the best options for you. Since a pregnancy is an even higher risk condition for a blood clot than hormones, you should definitely discuss the risks and benefits.
What can I do to minimize my risk, both in terms of medications to use or avoid and in lifestyle choices?
Dr. Emily: The biggest lifestyle measures are to be active, stop smoking and lose weight if you are overweight. Get up and move around when travelling long distances. Don’t cross your legs when you are seated. If you can’t get up, you can pump your calves by lifting up on your toes to keep the blood flowing in your calves. Discuss any medication questions with your doctor.
What are the signs that I might have a blood clot?
Dr. Emily: Pain, swelling, redness and warmth in a leg are all symptoms of a blood clot. It tends to be unilateral and it’s uncommon to have symptoms in both legs.
If I suspect a blood clot, should I head to the ER? When is my situation serious?
Dr. Emily: If you suspect you have a blood clot, you should seek immediate medical attention. Call your doctor and let them know you are concerned about a blood clot. You should be seen right away, but you don’t necessarily need to go to the Emergency room. If you can’t get into your doctor, you should go to the ER. If you are experiencing shortness of breath, chest pain or a racing heart, you should go to the ER as this can indicate that you have a pulmonary embolism.
If I have had a blood clot, will I have another? Should I never fly again?
Dr. Emily: You are definitely at higher risk to have a blood clot if you have previously had a blood clot. In fact, the biggest risk factor for having a blood clot is history of a prior blood clot. However, this doesn’t have to cramp your travel plans. Speak with your doctor about ways to minimize your risk.
If I have a blood clot, what can my doctor and/or I do about it?
Dr. Emily: Blood clots are treated with blood thinners. Newer medications have made this much simpler in recent years. In the past, you would be hospitalized for initial treatment and then continued on blood thinners that required frequent monitoring with blood tests. Some patients can take oral medications while others require injectable medications. New medications are available that can be given orally and do not require frequent blood tests.
Your doctor will advise the best treatment for you. Typically, treatment lasts between 3-6 months.
So, what is your takeaway from all this? Well, blood clots are not something to be taken lightly. If you have a history, personally or in your family, make sure your doc knows and it’s a part of your conversation. But if you are a healthy, non-smoking, postmenopausal woman who’s never had a blood clot, the benefits of HRT may well outweigh the risks. Be sure to explore all your options – types of HRT, doses, and delivery systems – with your doc.
MORE ABOUT THE DOC: Dr. Cooper is a board-certified internal medicine physician who has practiced in Seattle since 2004. She is passionate about developing lifelong relationships with her patients. She recently launched her own clinic, Sound Medicine and Wellness.
Have you ever had a blood clot or is this a concern for you? We’d love to hear how you’re thinking about it, so please feel free to share with the community by leaving us a comment below, or talking to us on our Facebook page or in Midlife & Menopause Solutions, our closed Facebook group.
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