While HRT can be highly effective, it does carry some risks. Long-term use—particularly combined estrogen and synthetic progestins—has been linked to slightly increased risks of blood clots, stroke, and in some cases, breast cancer.
For decades, HRT was widely considered safe and even recommended for preventing heart disease. This changed dramatically in 2002 when the Women's Health Initiative (WHI) study raised serious concerns about breast cancer and cardiovascular risks in women taking oral conjugated equine estrogens (oCEE) combined with synthetic progestogen.
These findings caused many women to stop HRT and made doctors much more cautious about prescribing it. However, further analysis revealed a more complex picture: the increased risks were mainly seen in women who started HRT after age 60 or more than 10 years past menopause.
Long-term follow-up from the WHI showed no difference in overall death rates between women on HRT and those taking placebo. Younger women who took estrogen-only therapy even showed survival benefits. Recent studies like the Kronos Early Estrogen Prevention Study (KEEPS) and the Early Versus Late Intervention Trial with Estradiol (ELITE) have confirmed that HRT has a favorable safety profile when started early in menopause.
The key takeaway? For healthy women under 60 or within 10 years of menopause, HRT is considered safe and provides meaningful benefits.
The safety of HRT also varies depending on personal factors such as age, weight, smoking habits, alcohol intake, family history, and existing health conditions. Certain medical conditions may make HRT unsuitable, including:
- Uncontrolled high blood pressure
- Active liver disease
- Blood clotting disorders
- Certain types of cancer
- Unexplained vaginal bleeding
Because every woman’s health profile is different, it’s essential to discuss your complete medical history with a menopause specialist who can tailor treatment to your specific needs and help you optimize benefits while minimizing risks through healthy lifestyle choices.
Breast Cancer Risk
Breast cancer is the most common concern women have about HRT. To put this in perspective: every woman has a baseline lifetime risk of developing breast cancer—about 1 in 8. HRT may slightly increase this risk, particularly with long-term use, but for most women the overall risk remains relatively low.
Several factors influence how much HRT might increase breast cancer risk:
- Type of HRT – estrogen-only therapy generally carries lower risk than combined therapy
- Duration of use – longer use is associated with higher risk
- Type of progestogen – bioidentical progesterone appears safer than synthetic versions.
It's important to remember that lifestyle factors often have a bigger impact on breast cancer risk than HRT. Being overweight, drinking alcohol regularly, and lack of physical activity typically increase risk more than hormone therapy itself. Discussing your individual risk factors—including family history, lifestyle, and personal health profile—with a knowledgeable healthcare provider will help you make the safest, most informed decision about whether HRT is right for you.
Uterine and Ovarian Cancer Risk
Uterine (Endometrial) Cancer
- Estrogen-only HRT increases uterine cancer risk because estrogen stimulates the uterine lining to grow. This is why women with an intact uterus must take a progestogen or use a Mirena coil—these provide crucial protection against dangerous overgrowth of the endometrium.
- Combined HRT (estrogen plus progestogen) actually reduces uterine cancer risk because the progestogen counteracts estrogen's stimulating effects on the uterine lining, keeping it healthy and protected.
Ovarian Cancer
The relationship between HRT and ovarian cancer is less straightforward:
- Estrogen-only HRT may slightly increase ovarian cancer risk according to some studies
- Combined HRT doesn't appear to increase risk and may even reduce it in some research, though findings vary
Personal factors significantly influence your cancer risk, including family history, previous cancers, smoking status, and overall health. Discussing these factors with a menopause specialist will help determine the safest HRT approach for your specific situation.
Risk of Progestogen Intolerance (Progesterone Intolerance)
Progesterone intolerance, also called progestogen intolerance, occurs when the nervous system has an exaggerated or hypersensitive response to progesterone—either naturally produced by the body or taken as part of HRT or other hormonal treatments. The two terms, “Progesterone intolerance” and “progestogen intolerance,” refer to the same condition and are often used interchangeably to describe a spectrum of negative reactions to progesterone or progestins.
Women with progestogen intolerance may experience:
- Severe mood changes or anxiety
- Extreme fatigue
- Intense bloating or breast tenderness
- Sleep disturbances
- Depression or irritability
These reactions can vary depending on the specific type or formulation of progestogen used.
Many women can still use progestogen successfully by working with their healthcare provider to find the right type and dose. Options might include:
- Switching from synthetic progestins to bioidentical progesterone
- Adjusting the dosage or timing
- Trying different delivery methods (oral, vaginal, or intrauterine)
Never adjust doses or switch products on your own. Making changes without medical guidance can lead to serious complications like irregular bleeding or dangerous changes to your uterine lining. A menopause specialist can help you find a solution that minimizes symptoms while maintaining essential protection.
Blood Clots and Stroke Risks
HRT can increase the risk of blood clots (deep vein thrombosis or pulmonary embolism) and stroke, but the level of risk varies significantly based on how you take your hormones and which types you use.
- Oral estrogen (pills) – carries higher risk of blood clots and stroke
- Transdermal estrogen (patches, gels, sprays) – much lower risk because hormones bypass the liver
- Hormone type – synthetic progestogens may slightly increase clot risk compared to bioidentical progesterone
Most women can safely use HRT by choosing the right formulation. However, certain factors, including smoking, being overweight, or a personal or family history of blood clots, can further elevate the risk. Your healthcare provider can assess your individual risk factors and recommend the safest approach for your specific situation.
Risk of Gallbladder Disease
HRT can slightly increase your risk of gallbladder problems, but the way you take it matters. Oral estrogen (pills) carries a higher risk because it passes through the liver, which can promote gallstone formation. Transdermal estrogen (patches, gels, or sprays) bypasses the liver entirely and enters your bloodstream directly, significantly reducing this risk.
Your personal risk is also influenced by age, weight, and family history of gallstones. Discuss these factors with your healthcare provider to choose the safest HRT option that maximizes benefits while minimizing gallbladder risk.