Estriol: The "Good" Estrogen
James Biddle M.D.

Do you know a woman with breast cancer? Unfortunately, too many of us do, since cancer rates are rising at an alarming pace.

Survivors of breast cancer face many challenges, including the management of menopausal symptoms. One particular dilemma is the question of whether or not to use Hormone Replacement Therapy (HRT), especially estrogens.

Many breast cancer patients are menopausal, while most others usually experience menopause during treatment. As they face the stress of cancer and its treatment, these women also suffer menopausal symptoms of hot flashes, night sweats, sleep deprivation, irritability, decreased sex drive, and vaginal dryness, as well as an increased risk of osteoporosis. However, they are routinely denied Hormone Replacement Therapy due to fears that the hormones will increase the risk of cancer recurrence.

I recently received a letter from an oncologist of one such patient. Now in her late fifties, she had a mastectomy for breast cancer over ten years ago, then went thru early menopause from the treatments. Her symptoms continue today, many of which might be helped with hormones. However, her oncologist insists that she remain hormone deficient.

Many women never fully regain an optimal quality of life without hormones. The good news is that by using the "right" hormones, we might gain the benefits of HRT without increasing cancer recurrence. In fact, we may even decrease recurrence by improving the balance estrogens.

Women’s bodies have a natural balance of weak and strong estrogens, with much higher levels of weak estrogens than strong estrogens. The strong estrogens, known as E1 and E2 (estrone and estradiol), cause breast cells to divide, increasing the risk of those cells turning cancerous. The weak estrogen called E3, or estriol, blocks out the strong estrogens at the receptor sites of breast cells, thereby decreasing cell division and the risk of cancerous transformation.

Way back in 1966, an article in JAMA (the Journal of the American Medical Association) entitled "Reduced Estriol Excretion in Patients with Breast Cancer" showed that breast cancer patients had more strong estrogens and less of the weak estrogen than women who don’t get breast cancer.

Therefore, the strong estrogens are only bad when they are out of balance with the weak estrogens. Interestingly, fat cells produce strong estrogens, explaining why heavier women get more breast cancer.

Unfortunately, when prescribing hormones, physicians are trained to use only the strong estrogens, so naturally they shouldn’t give those to women with breast cancer. However, in 1978 a persuasive editorial in JAMA entitled "Estriol, the Forgotten Estrogen" provided support for the use of estriol after cancer. By giving estriol or E3, we can increase the weak estrogens and block out the strong estrogens, theoretically decreasing the risk for cancer while improving the quality of life.

Although good news sometimes travels slowly within medicine, estriol and other natural hormones are available by prescription.

Lemon HM et al. Reduced estriol excretion in patients with breast cancer prior to endocrine therapy. JAMA 1966; 196(13):112-120.

Follingstad AH. Estriol, the forgotten estrogen? JAMA 1978;239(1):29-30