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HRT Causes Cancer

The belief that HRT causes cancer is a common and deeply persistent myth, but the real story is more nuanced.

Some types of hormone replacement therapy can increase the risk of certain cancers, but HRT is not uniformly dangerous, and in some cases it may even reduce the risk of other conditions. The risk depends heavily on the type of HRT, the duration of use, and the individual patient’s medical background.

What We Used to Think

After major headlines in the early 2000s, many people came to believe that:

  • HRT is inherently unsafe
  • Taking hormones after menopause “causes cancer”
  • HRT should be avoided entirely
  • Menopause symptoms should be endured rather than treated

For many women, these fears led to sudden discontinuation of therapy and a general stigma around menopausal treatment.

When It Was Disproved

In the 2000s, follow-up analyses of major studies—especially the Women’s Health Initiative (WHI)—clarified that the initial public messaging was overly simplified.

Researchers found that:

  • Risk differed between combined estrogen-progestin therapy and estrogen-only therapy
  • Age and timing mattered (starting HRT closer to menopause carried different risks than starting much later)
  • The absolute risk increase for many people was smaller than headlines implied

Rather than proving that “HRT causes cancer,” the evidence showed that some forms of HRT modestly increase risk in some contexts, while other forms may not.

Why It’s Wrong

  • Not all HRT is the same: Estrogen-only HRT (typically used after hysterectomy) and combined HRT (estrogen + progestin) have different risk profiles.
  • Breast cancer risk is specific, not universal: Combined estrogen-progestin therapy is associated with a modestly increased risk of breast cancer, particularly with longer use.
  • Estrogen-only therapy may not raise breast cancer risk in the same way: Some evidence suggests estrogen-only HRT may have little effect on breast cancer risk, or may reduce it in certain populations.
  • Other cancer risks vary: HRT can reduce the risk of some conditions (such as osteoporosis) but may increase the risk of others (such as endometrial cancer if estrogen is taken without progesterone in women with a uterus).
  • Absolute risk matters: Many discussions confuse relative risk with absolute risk, leading to exaggerated fears.

In short: HRT is not “cancer-causing” in a blanket sense. It has tradeoffs that must be evaluated case-by-case.

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