Your ovaries begin producing progesterone just prior to ovulation, increasing output for approximately two weeks. If you don't conceive, your progesterone levels will plummet because there is no fertilized egg to support. Since progesterone causes the lining of the uterus to thicken in anticipation of pregnancy, when progesterone wanes, the uterus sheds that lining and menstruation occurs. If you conceive, the corpus luteum--what remains of the follicle after the egg is released--will keep producing progesterone and the hormone will continue to build and nourish the uterine wall to allow the embryo to implant there and receive nourishment.
Clarification
The terms progesterone and progestin are not the same thing. Progesterone is first produced in your ovaries and maintains a regular, healthy menstrual cycle. When pregnancy occurs, the placenta takes over production of progesterone and this is integral to your baby's development. Progestins are synthetic versions of progesterone, administered by your health care provider to increase your progesterone level if it falls too low. According to Dr. Frederick Jelovsek for the website Women's Health Resource, the inability of progesterone to be orally absorbed into the body prompted the creation of progestins.
Process
After progesterone is produced by the ovaries or the placenta, it is released into the bloodstream where it is carried to receptors throughout your body. Here, it can begin to carry out its various functions. The website SafeMenopauseSolutions.com says that once progesterone reaches its receptors, adequate levels of progesterone will maintain the uterine lining to sustain and nourish your baby throughout your pregnancy. It is also important to other body functions.
Functions
Progesterone counteracts estrogen, which has cancer-promoting properties that can potentially affect the lining of the uterus, called the endometrium. Once progesterone reaches the proper receptors, it also fights stress, induces sleep and builds strong bones. It is a component of birth control pills. Jelovsek says that the synthetic progestin can elevate progesterone levels so that your body believes you have conceived and interrupts ovulation. Progestin helps the uterus get ready to receive a fertilized egg so it is beneficial to fertility treatments, according to the website SafeMenopauseSolutions.com.
Time Frames
Progesterone levels should rise continuously throughout pregnancy, according to SafeMenopauseSolutions.com. They can triple during the first few weeks of pregnancy, and when the uterus takes over the production in the second trimester, the end effect can be progesterone levels up to 15 times more than that in ovulating, non-pregnant women. As women age, they may not ovulate in all monthly cycles. Without regular ovulation, progesterone decreases through perimenopause and menopause and is lost almost entirely by the time a women reaches post-menopause. When the ovaries no longer produce progesterone, the adrenal cortex of the brain is capable of taking over. But the website Project Aware warns that Western women have depleted adrenal glands that might be inadequate to take over the functions of progesterone in the body.
Other Advantages
Jelovsek also says that when the body is producing high levels of progesterone, it can have a sedating effect. This can work to relieve epileptic symptoms and to reduce the likelihood of uterine contractions during pregnancy that can result in premature labor. According to Jelovsek, epileptic women have a marked reduction in seizures during periods in their monthly cycles when their progesterone levels are elevated.
