There is great confusion in the media, the general public, and even among doctors about the natural bioidentical hormone called progesterone and the drugs called “progestins.” When I see a new female patient who would benefit from progesterone, I typically have to explain what progesterone is, what it does naturally in the body, and how it is different from the synthetic drugs called progestins. To learn more about our hormone replacement and balancing options for women, please click here: Female Hormone Replacement.
Here is the simple explanation:
Progesterone: A hormone made by a woman’s ovaries which has healthy beneficial effects all over her body, including her brain, her breasts, her bones, her arteries, and her uterus, where it, in combination with the natural bioidentical hormone estradiol regulates her menstrual cycles and allows her to become pregnant and carry a child to term. The word progesterone is a combination of “Pro” (allowing for) and Gesterone (ie, gestation or pregnancy), it is well known for allowing gestation or pregnancy although it has many other benefits. It is commonly used in fertility clinics to help a pregnant woman maintain her pregnancy.
Women with a deficiency of progesterone may have difficulty conceiving and maintaining a pregnancy; they typically also have bad PMS and heavy, painful periods, insomnia, excessive anxiety, and tender, enlarged, fibrocystic breasts. Women with low progesterone typically gain excess weight and feel bloated. Endometriosis, fibrocystic disease of the breasts, and uterus fibroid growths and abnormal heavy bleeding at periods are common in women who don’t have enough progesterone. In my practice, proper treatment of women with progesterone deficiency has greatly improved their health and quality of life. Balancing progesterone helps women get a deep restful sleep, reduce breast lumps and tenderness, stop heavy periods, regulate irregular cycles, relieve PMS mood symptoms, reduce anxiety, help with weight loss and stop the bloated feeling. Progesterone supplementation likely reduces a woman’s risk of developing breast cancer, based on the scientific literature.
However, natural progesterone has many other benefits to a woman.  Progesterone improves brain cell function and repair, improves memory, helps induce sleep and has a calming effect on moods, like a natural valium, by enhancing the brain neurotransmitter GABA activity. Progesterone inhibits abnormal cell growth and even breast cancer cells by turning on natural anticancer genes called P53 and BCL-2.
Progesterone has a similar inhibitory effect on other cancers such ovarian cancer and even endometrial cancer. It is truly an anticancer bioidentical hormone!
There is much more that can be said in praise of progesterone and really, there is no downside to it in my experience, if dosed appropriately.
Now Progestins:
Progestins are chemicals that have a progesterone-like chemical structure and some of progesterone’s effects but which are made by a pharmaceutical company and are sold as drugs such as medroxyprogesterone, norethindrone, levonorgestrel, etc. Progestins are not natural hormones and should not be lumped together with progesterone or estrogens which are natural hormones although they typically are. Thus the confusion. If you search for lists of progestins, you will commonly see natural progesterone included even though it is NOT technically a drug or a progestin. It is a natural hormone. This is confusing to patients as well as doctors.
Progestin drugs are primarily developed and marketed because they can be patented and thus are very profitable for big pharma (vs progesterone, which cannot be patented because it is a natural hormone). They also, as synthetic drugs, can have some useful drug characteristics vs. natural progesterone; however the progestins often have unwanted adverse effects as well.
Progestins are commonly found in oral contraceptive pills and the IUDs known as Mirena and Kyleena.  One thing they do really well is stop ovulation and thus prevent pregnancy and can also be useful to stop excessive uterine bleeding as they are much more powerful than natural progesterone in that aspect. I have occasionally prescribed medroxyprogesterone (Provera) to stop breakthrough uterine bleeding and it works quite well when natural progesterone is not potent enough. Women typically have this sort of bleeding from a fibroid tumor or a uterine polyp; women with a normal uterus do not normally need a progestin to prevent breakthrough bleeding; natural progesterone works quite well for this in natural bioidentical hormone replacement therapy. The side effects of the progestins (not progesterone) are also of concern.  Progestins can cause cardiovascular damage and damage the arteries and increase the risk of a heart attack (discovered in the famous WHI study), where progesterone does not. Progestins do not calm the brain and reduce anxiety as does natural bioidentical progesterone. They do not inhibit breast cancer cells as does natural progesterone; in fact some progestins may actually increase the risk of breast cancer.
So the word progestin should not be used interchangeably with progesterone, as they commonly are, even in medical articles. When reading an article that claims to show some adverse effect from progesterone, I always check to see exactly what drug they were giving the patients. Invariable, if there is an adverse effect being attributed to “progestins or progesterone”, when you really look closely at the data, they are actually seeing adverse effects from progestins-not natural progesterone. I have yet to see any article proving that natural, bioidentical progesterone is causing any adverse effect in menopausal women.
