Unraveling the Myths of Hormone Replacement Therapy and Cancer

There is a good chance you have heard that hormone replacement therapy (HRT) or hormone therapy (HT) causes cancer. If you have a family medical history that includes cancer, you have almost certainly been told by a physician that HRT carries a high risk.

Unfortunately, this is a wildly dangerous myth being propagated by countless physicians based on a study from 2002, called the Women’s Health Initiative (WHI). What you should know right away is the study has been largely disproven. 


Unraveling the Information Regarding Hormone Replacement & Cancer Risk

When discussing hormone replacement therapy, it is not uncommon to hear someone voice the concern, “But don’t hormones cause cancer?”Unfortunately, despite multiple studies over many decades refuting this claim, this belief persists – in large part as a result of a single study published in 2002 called the Women’s Health Initiative. The published article suggested that post-menopausal women taking a combination of estrogen and progestin were at an increased risk for heart disease, stroke, cancer, and blood clots. However, what is often overlooked is this study’s finding that also showed that those taking estrogen alone showed no increased risk. Taken together, the study indicated that it was the progestin, a synthetic form of progesterone (as opposed to the natural hormone progesterone), which led to increased risks – not the estrogen.

The 2002 study became widespread, and with it, concerns about hormone replacement therapy (HRT). Over the following years, there was a drastic drop in HRT usage as a result of the WHI. In 1999-2000, the total use rate of HRT in the United States was 38.3%, and in 2003, Norway and Sweden saw a 70% drop in HRT use. 

After the widespread discontinuation of hormone therapy, some interesting trends emerged. The decrease in hormone replacement yielded opposite outcomes than originally expected. 2004 to 2005 saw an increase in age-adjusted osteoporosis, a condition well-documented as linked to age-related decline in hormones. . Additionally, breast cancer rates remained unchanged.

After observing the opposite outcomes of stopping hormone therapy, doctors and physicians decided to analyze more data and re-evaluate the 2002 study. Further investigation of the original study yielded inconsistencies and potential biases. Of those in the original 2002 study, 50% were smokers, 50% were fat or obese, and for some women 10-20 years into menopause, the damages had already occurred. Overall, the majority of the original subjects had increased symptomatology due to their current lifestyles, not due to hormone replacement therapy.

Evidence refuting the 2002 article was also compiled. A 2003 update to the 2002 study showed no such hormone-induced increase in breast cancer. Additionally, evidence of the delivery of the hormones was shown to affect risks. Oral estrogen, such as found in birth control, shows an increased risk of blood clots and venous thrombosis, with no change in mortality. However, oral estrogen is filtered through the liver, which causes the increased risk. Transdermal estrogen, the type used in bioidentical hormone therapy, bypasses the liver and therefore eliminates the risk associated with oral estrogen. Evidence suggests it may even reduce the risk of blood clots and venous thrombosis. Similarly, bioidentical progesterone, unlike the synthetic progestin, has been well researched and documented for its many health benefits from sleep to weight management and more. 

Sadly, even today, many physicians as well as the United States Preventive Services Task Force (USPSTF) advise against such therapies based on the original 2002 results. Overall, bioidentical hormone replacement therapy is a sex-specific therapy meant to aid in the reduction of breast cancer, bone fractures, cancer mortality, and more. While a single early 2002 study suggested an increased cancer and blood-clot risk, dozens more recent studies have refuted such claims. Hormone therapies are available as an aid to women and men in maintaining their physiological health without increased risks – and arguably are critical to healthy aging and overcoming the traditional decline associated with reduced hormone levels as we age.


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