Progesterone is a term that is incorrectly used interchangeably to describe both progesterone which is "chemically identical" to what the body naturally produces, and synthetic derivatives. Synthetic progestins are analogues of progesterone, and have been developed because they are patentable, more potent, and have a longer duration. Medroxyprogesterone acetate, the most commonly used synthetic progestin, was shown in a large study to cause significant lowering of HDL "good" cholesterol, thereby decreasing the cardioprotective benefit of estrogen therapy. Side effects are a frequent cause for discontinuation of HRT. Only about 20% of women who start synthetic HRT remain on it two years later.
- is commonly prescribed for perimenopausal women to counteract "estrogen dominance" which occurs when a woman produces smaller amounts of progesterone than normal relative to estrogen levels.
- alone, or combined with estrogen, may improve Bone Mineral Density.
- minimizes the risk of endometrial cancer in women who are receiving estrogen.
- is preferred by women who had previously taken synthetic progestins.
The benefits of progesterone are not limited to prevention of endometrial cancer in women who are receiving estrogen replacement. Progesterone therapy is not only needed by women who have an "intact uterus", but is also valuable for women who have had a hysterectomy. Vasomotor flushing is the most bothersome complaint of menopause, and is the most common reason women seek HRT and remain compliant. For over 40 years, estrogens have been the mainstay of treatment of hot flashes, but progesterone may be effective as well.