- Preventing or Treating Osteoporosis
- “Opposing” Estrogen
Progesterone is one of the two primary female hormones. As the name implies, progesterone prepares ("pro") the womb for pregnancy (gestation). Progesterone works in tandem with estrogen ; indeed, if estrogen is taken as a medication without being balanced by progesterone (so called unopposed estrogen), there is an increased risk of uterine cancer.
However, progesterone is not well absorbed orally. For this reason, pharmaceutical manufacturers developed "progestins," substances similar to progesterone which are more easily absorbed. Most of the time, a woman prescribed "progesterone" is really being given a progestin. Two of the most commonly used progestins are medroxyprogesterone and norethindrone. However, it has been suggested that actual progesterone may offer benefits over progestins, such as fewer side effects.
Progesterone can be absorbed through the skin to some extent, and some alternative practitioners have, for years, promoted the use of progesterone creams. Such progesterone creams are typically, but misleadingly, said to contain "natural" progesterone. This is an oddly chosen term, as the progesterone in these creams is actually produced in a laboratory, just like other synthetic hormones. To avoid confusion in this article, we will call progesterone "true" progesterone, or just "progesterone."
Besides creams, a special form of true progesterone that can be absorbed orally, micronized progesterone, has recently become available as a prescription drug.
Inconsistent evidence suggests that progesterone cream might help reduce menopausal symptoms. However, it does not appear to be strong enough to balance the effects of estrogen, thus reducing the risk of uterine cancer. (Oral micronized progesterone is strong enough for this purpose.) Contrary to numerous books and magazine articles, there is no more than weak, inconsistent evidence that progesterone cream offers any benefits for osteoporosis.
Progesterone is synthesized in the body and is not found in appreciable quantities in food. For use as a drug or dietary supplement, progesterone is synthesized from chemicals found in soy or Mexican yam .
Note: Another aspect of the widespread misinformation involving progesterone cream is the concept that Mexican yam itself contains progesterone, or substances that the body can convert into progesterone. This is incorrect. Industrial chemists can convert a constituent of Mexican yam (diosgenin) into progesterone, but only by using chemical pathways not found in the body.
Like progestins, oral progesterone protects the uterus from the stimulating effects of unopposed estrogen. However, standard doses of progesterone cream probably provide too little progesterone to serve for this purpose (see next section).
What Is the Scientific Evidence for Progesterone?
Despite widespread reporting that true progesterone is effective for treating or preventing osteoporosis, the evidence for such an effect is at best inconsistent.
Even though progesterone is sold as a dietary supplement, it is a hormone, not a food. We recommend that it not be used except under physician supervision.
- Reviewer: EBSCO CAM Review Board
- Review Date: 07/2012 -
- Update Date: 07/25/2012 -