There is a natural decline of sex hormones as a woman ages. Testosterone is the dominant hormone in young healthy women and is five to 20 times more abundant than estrogen. Yet as women age and enter menopause we chose estrogen as a primary hormone for replacement. It is more or less a guess.
In the 1940s they found that taking sheep ovaries and grinding them up would give women relief of menopausal symptoms. Then they discovered they could extract estrogen from the urine of a five-year-old pregnant horse, and that the estrogen relieved menopause symptoms. (The brand name Premarin stands for PREgnant MARe urine.)
In 2002, it was discovered that woman on Premarin and Provera, the biggest-selling drugs at the time, had a slight increase in the risk of breast cancer. This led to a 50% drop in the use of hormone replacement therapy.
There’s a lot to this story, and I talk about it in my book, Testosterone: Strong Enough for a Man, Made for a Woman. But here I’ll talk specifically about how perhaps testosterone should have been the hormone we were replacing, and how testosterone substantially reduces a woman’s risk of developing breast cancer.
Early animal studies showed that testosterone worked better than anticancer drugs for suppressing the development of breast cancer growth, called breast cell proliferation.
(Menopause Vol 10, No. 4, 2003)
Later studies evaluated about 100 women and the effect of hormone replacement on the breast over six months. Estrogen is known to stimulate breast cell proliferation, which can be thought of as a precursor to the possible development of breast cancer. Testosterone had been shown to reduce or lessen that proliferation of the breast.
In this study, the women were put on estrogen and their breast cell proliferation was evaluated. There was an increase by 500%. When testosterone was added, breast cell proliferation completely stopped.
(Menopause, Vol. 14, No. 2, 2007)
So these studies showed that testosterone would block proliferation of breast tissue. What about the effect of testosterone when combined with hormone replacement in the actual development of breast cancer?
Breast cancer is relatively common. About one in seven women will ultimately develop breast cancer, most commonly after age 50.
There is a statistical measurement that is commonly used for evaluating rates of breast cancer called “100,000 woman-years.” This is a means of comparing interventions. For example, it could be the study of 100,000 women for one year, or 10,000 women for 10 years. When comparing statistics, researchers use math to get to the 100,000 woman-year measurement.
In large clinical studies, breast cancer rates with or without hormone replacement is about 350-520 per 100,000 woman-years.
There were two types of conventional hormone replacement therapy. Estrogen alone was used in women with a prior hysterectomy. Estrogen and progestin were used when the woman’s uterus was intact. The purpose of the progestin is to prevent menstruation.
Progestin is an artificial drug that acts like progesterone the hormone, to protect the uterus. Progestin in and of itself has a link to breast cancer. Progesterone does not. In other words, progesterone the hormone is breast cancer protective, and progestin the drug has a slight stimulation of breast cancer.
An Australian study added testosterone to the conventional estrogen/progestin hormone replacement therapy. They found that adding testosterone to estrogen and progestin reduced the breast cancer rate to 293 per 100,000 woman-years.
Even more remarkable, in women on estrogen and testosterone only (without the progestin drug), the rates of breast cancer fell to 115 per 100,000 woman-years. That’s about a 75% reduction.
(Menopause: The Journal of The North American Menopause Society
Vol. 11, No. 5, pp. 531-535, 2004)
Taking this further, a five-year study was reported on the use of testosterone only for women in pre-menopause as well as post-menopause.
Testosterone is the dominant hormone in a young healthy woman. And testosterone can be converted into estrogen by an enzyme called aromatase. This is done at the cellular level. The idea is that if a woman is given testosterone, she can convert it into estrogen where needed, which is what happens naturally in the body.
In this study the women were given testosterone implants. It’s called a pellet and is about the size of a grain of rice. It’s inserted under the skin and breaks down naturally over about three months.
In this very large study, all symptoms of menopause or pre-menopause were improved. There were no adverse drug events.
The breast cancer rate in the geographic area where this study occurred is about 300 per 100,000 woman-years. Women who continued to use testosterone during the five years had a reduced incidence of breast cancer of 73 per 100,000 woman-years. That’s about a 75% reduction in the rate of breast cancer.
(Maturitas 76 (2013) 342– 349)
Testosterone, with or without estrogen, is effective for relief of menopause or perimenopause symptoms. Progesterone the hormone (not progestin the drug) should be used where needed. Alone or together these hormones improve quality of life as well as improve all symptoms of menopause including:
- hot flashes
- sleep disturbance
- heart discomfort
- depressive mood
Premenstrual Syndrome Symptoms
- memory loss
- migraine headaches
- vaginal dryness
- sexual problems
- bone pain and loss
If you would like to consider hormone replacement to improve the symptoms associated with hormone decline, but are concerned about health risks, I hope this answers some questions.
While there are some health risks associated with taking hormone replacement drugs, particularly when starting them at a much older age, this risk does not occur with actual hormones. In fact, the risk of breast cancer, heart disease and other diseases associated with aging declines with actual hormone replacement.
If you are interested in having your hormones evaluated, please call us at 586-992-8300.
Dr. Charles Mok