What is Progesterone?
Progesterone is a women steroid hormone responsible for the changes in the endometrium in the second half of the menstrual cycle. Progesterone prepares the lining of the uterus (endo-metrium) for implantation of a fertilized egg and its development, and maintains the uterus throughout pregnancy.

Progesterone Production:
Progesterone is found in relatively low levels for the first part of a woman's menstrual cycle. It is produced by cells within the ovaries called "granulosa cells" which surround the tiny follicles that will mature to become ovulated eggs.

After ovulation, the "yellow body" (corpus luteum) that released the mature egg into the fallopian tube begins to secrete high levels of progesterone from the granulosa cells within it. This hormone stimulates the growth of rich blood vessels that supply the uterus lining (endometrium). It also causes the expansion of tiny glands in the endometrium that produce a fluid (uterine fluid) that can be used to nourish sperms and embryos that find their way into the uterus. These tiny glands are created by the estrogen hormone and the progesterone takes over the job of making them mature into "feeding structures".

The production of progesterone will normally drop away after about 10 days beyond ovulation. It is this sudden reduction in the hormone that will prompt the menstruation period to begin due to the reduced oxygen supply from the blood vessels that were previously encouraged to grow by the progesterone hormone.

Natural Progesterone in Fertility & Pregnancy:
The proper amount of natural progesterone is crucial to a woman who is trying to become pregnant. Natural Progesterone prepares the uterine wall for implantation of the fertilized egg. Without adequate progesterone, the egg will be expelled. Natural Progesterone treatment can also be used to induce fertility when there appears to be ovulatory dysfunction.

During the pregnancy, the progesterone is needed in the following ways, (mostly in conjunction with estrogen):
• 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)

Because progesterone is essential to prevent the premature shedding of the supportive secretory endometrium, a significant drop in progesterone levels or blockade of progesterone receptor sites during the first 10 - 12 weeks of pregnancy may result in the loss of the embryo (miscarriage).

At the end of the pregnancy, the levels of progesterone secreted by the placenta drop off. It is this action that stimulates the beginning of the contractions that will lead to birth.

Low Progesterone Symptoms:
The symptoms on a woman due to low levels of natural progesterone can include any or all of the following:

Natural Hormones: Estrogen · Progesterone · Testosterone · Bioidentical
Treatments · HRT