Progesterone Information

What is Progesterone?
Progesterone is a female hormone produced by the ovaries. It plays a vital role in both ovulation and pregnancy. After an egg is released from your ovaries, the remaining follicle becomes the corpus luteum. The corpus luteum secretes estrogen which, in turn, produces progesterone. This progesterone softens your uterine lining, helping with implantation.
Progesterone is not produced in the body at all until ovulation has occurred. The sac which held the released egg becomes the corpus luteum. The corpus luteum is responsible for releasing progesterone (there is no other endogenous- natural human- source of progesterone), and will only do so for about 2 weeks. It is the progesterone which changes the structure of the inner lining of the uterus and prepares it to shed. When progesterone is no longer being made by the corpus luteum, the muscle of the uterus spasms/contracts, and the inner lining of the uterus is sloughed off, causing menses occurs.
Progesterone is a hormone that is necessary to have a successful pregnancy. Without the right levels of progesterone, it is possible that you will have difficulties conceiving or carrying a pregnancy to term. If you are experiencing unexplained infertility, mutliple miscarriages, or if you are taking fertility drugs, a progesterone test may be helpful, done at 7dpo.

Your reproductive endocrinologist can use the results of your progesterone test to help determine any underlying reproductive endocrinologist can use the results of your progesterone test to help determine any underlying health problems that may be contributing to infertility.

Provera/Prometrium Usage:
Provera is an exogenous source of progesterone and will behave in a way that mimics the progesterone released by a normal corpus luteum.

The catch to provera/progesterone causing menses, is that the inner lining of the uterus must first be built up by estrogen before it can be changed and prepared to be sloughed off.
Also, if the lining is built up too much by estrogen, and there is no progesterone, then sometimes it just gets too thick and will begin to break off on its own, which is the reason for anovulatory bleeding.

Progesterone in Pregnancy

It gives your body progesterone in preparation for carrying a baby. Once you are pregnant your body doesn't start producing progesterone until the baby is a little further along and the placenta takes over in production. Here are some things I found online.

  • Makes the endometrium develop and secrete fluids after being primed by estrogen
  • Maintains the functions of the placenta and fights off unwanted cells near the womb that could cause damage to the placenta or foetus.
  • Keeps the endometrium in a thickened condition
  • Stops the uterus making spontaneous movements
  • Stimulates the growth of breast tissue
  • Prevents lactation until after the birth (with estrogen)
  • Strengthens the mucus plug covering the cervix to prevent infection.
  • Strengthens the pelvic walls in preparation for labour.
  • Stops the uterus from contracting (thus keeping the baby where it is)