Use of Progesterone and Breast Cancer?

Dear JPC,

Those are great questions. The dosage in milligrams is very different between hormone replacement therapy and the birth control pill. But the factor that is important is physiological activity – or how much it affects the body. The hormone replacement therapy is designed to try to give the woman’s body a dose that would act about the same as the hormones she was previously making – trying to give a post menopausal woman with the same level of hormones as a woman in her reproductive years. The birth control pill is trying to suppress a woman’s normal function. To consistently try to shut her fertility down to prevent pregnancy in a reliable fashion takes about ten times the potency of the hormones a healthy woman’s body makes. Even though the doses of the synthetic progestins looks very small, they are formulated in the lab with a special bond, a carbon triple bond or alkyne, that the body is not designed to breakdown. So, the hormone stays in the body much longer ( as well as in the water supply). The bio identical hormones are broken down in hours, and if given for suppression of ovulation would have to be given several times a day.

You are right – any hormone, if given at the wrong dose, has risks. Insulin can save the life of a diabetic at the right dose, and can kill them if too high. The goal of hormone therapy is to get into the normal range. For progesterone, that range will vary with each day of the menstrual cycle, as well as with each week of pregnancy. Women with PMS typically have lower than normal progesterone and it is the usual practice of NaProTechnology medical consultants to check a woman’s baseline progesterone level during the post peak phase to see if it is low before supplementing with bio – identical progesterone. The same is also true of a woman at increased risk of miscarriage – the levels should be followed closely throughout the pregnancy, and the dose of progesterone is based on what is needed to get her in the range of a healthy pregnancy. Replacing progesterone when deficient is much different than giving so much that a woman’s body is suppressed, like with the hormonal contraceptives.

For women with breast cancer, progesterone supplementation is not recommended. However, for women at risk for breast cancer, the story is more complicated. Of the women who used NFP, and later developed breast cancer, looking back at their earlier mid luteal progesterone showed that they had much lower levels than women who did not develop breast cancer. This also fits with the research on the increased risk infertility poses for breast cancer. If you break the infertile group into those infertile due to mechanical problems like blocked tubes, versus those with hormonal problems and low progesterone, the women that develop the breast cancer are mostly those with the hormonal deficiency. After a first full term pregnancy, a woman’s risk of breast cancer goes down. The elevated hormones during pregnancy, including progesterone, lead to a maturation of breast tissue which makes them more resistant to carcinogens. However, during that first full term pregnancy, there is a slight risk that the elevated progesterone could enhance the growth of a tumor.

Clearly more research needs to be done, but all hormones should be used in the right context with careful thought.

You have brought up some great points – I hope I’ve answered your questions, but if not, let me know and we can continue the discussion.

Sincerely,

Lynn Keenan, MD