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Thoughts on progesterone
It has long been known that progesterone plays a major role in supporting pregnancy. If the ovary producing progesterone during pregnancy is removed, a miscarriage will result. Progesterone affects a woman's immune system, possibly by suppressing it in a manner that prevents a woman's body from rejecting the fetus as foreign. Progesterone plays a role in the onset of labor and abnormalities in progesterone production may cause some cases of pre-term labor.
Although there is a range of what constitutes a normal progesterone level, because of all of the above issues, we desire that our patients' progesterone levels be in the upper range of what is normal. We frequently supplement a woman's progesterone level and measure it after pregnancy is achieved. As pregnancy progresses, the placenta should be able to produce large quantities of progesterone. Sometimes when the placenta is slow to take this role, the pregnancy may not do very well.
In support of pregnancy, only progesterone should be used and not other drugs that act like progesterone such as provera or norithindrone. Many studies have shown that oral progesterone products have undependable absorption (depending on diet, etc.) as well as a short duration of action. Progesterone needs to be taken by a non-oral route. We occasionally use IM progesterone (taken as a shot). There is data that suggests an improved IVF outcome when progesterone is taken this way. However, it is an extremely unpleasant way to take progesterone. IM progesterone is dissolved in oil and the shot is a large one through a large diameter needle.
We feel that the best way to take progesterone is vaginally. It has been shown that this results in higher tissue levels in the uterus than any other method. We primarily use either Crinone or micronized progesterone (marketed to for oral use) taken vaginally. A newer product is endometrin which is also a vaginally administered product. There is less build up in the vaginal with Endometrin than with Crinone or micronized progesterone. These products generally stay in the vagina and release progesterone into the body continuously. We don't use progesterone suppositories as these rapidly run out of the vagina and thus cannot compensate for the short duration in which progesterone is metabolized by the body. There are other approaches for delivering progesterone to the body, but there is little or no data on using them in fertility applications.