Hormones and Breast Health

Hormones come up in almost every conversation about breast health, and the advice women read is often confusing. In this video, I'll explain what oestrogen does in the breast; what the evidence on HRT really means for your risk; and what changes after a diagnosis. Breast tissue is designed to respond to hormones, which is why it changes through each month and across your life. Oestrogen and progesterone work by attaching to receptors inside breast cells, and these receptors act a little like switches that tell the cells to grow. Around four in five breast cancers carry these same oestrogen receptors, which is what we mean by oestrogen receptor positive. That's important, because it means treatment can work by blocking or removing the oestrogen signal that the cancer cells rely on to grow. After a diagnosis, your pathology report will usually check the cancer for three things: receptors for oestrogen; receptors for progesterone; and a protein called HER2. HER2 is found in extra amounts in some cancers and has its own targeted treatments. A cancer with none of these three is called triple negative, and chemotherapy then plays a larger part. Where the body’s oestrogen comes from also changes over the course of your life. Before the menopause it’s made mainly by the ovaries, but afterwards most of it is made in fat tissue, by an enzyme called aromatase. That’s why body weight affects breast cancer risk after the menopause, and why medicines that block aromatase are used in treatment. HRT adds hormones on top of the body’s own; so it’s natural to ask what it does to breast cancer risk. Five years of oestrogen with a daily progestogen, starting at 50, is linked with around one extra breast cancer in every fifty women by the age of 70. And using it for less than a year adds very little risk. You may read that combined HRT more than doubles the risk of breast cancer, and both figures are true. The doubling describes the risk while a woman is taking HRT, whereas the one in fifty spreads that extra risk across twenty years. The type of HRT matters as well; and the evidence suggests the progestogen part drives most of the extra risk rather than the oestrogen. Body-identical progesterone looks reassuring for up to five years of use, although that isn't the same as having no risk at all. Whichever type you use, if you still have a womb, you'll need a progestogen alongside the oestrogen, because it protects the womb lining from cancer. Patches and gels avoid the small increase in blood clots seen with tablets. Your doctor may also suggest reviewing HRT each year, since the extra risk depends on how long you take it. Vaginal oestrogen, used as a cream, pessary or ring, is quite different from HRT that acts on the whole body. It gives a very low dose that works where it's applied. Large studies haven't found any increase in breast cancer risk from it in women who haven't had breast cancer. Things change after a breast cancer diagnosis; when HRT that acts on the whole body isn't recommended. For vaginal dryness, moisturisers and lubricants are the first step, and vaginal oestrogen may be considered alongside tamoxifen but generally not with an aromatase inhibitor. And that's a decision we'd make together with you. If you take tamoxifen, some antidepressants used to ease hot flushes can stop it working properly, so please check with your breast team before starting anything new. Please also mention any vaginal or urinary symptoms, even if nobody asks, because they usually respond well to treatment. Hormonal contraception, including the pill, carries a small extra risk of breast cancer while it's being used, and this fades after stopping . Because breast cancer is uncommon in younger women, the actual number of extra cases is very small, particularly for women in their teens and twenties. Our booklet sets out the full figures, and the British Menopause Society is a reliable source on the menopause and HRT. If you'd like to talk through what this might mean for you, please get in touch with me or my team.