In women who are not pregnant, progesterone prepares the endometrium, or lining of the uterus, for implantation by the fertilized egg.
This is the point approximately midway through a normal menstrual cycle when an egg is released from one follicle in your ovary.
After releasing the egg, the follicle is known as the corpus luteum, and begins producing increasing levels of progesterone.
This progesterone acts on the endometrium to make it thicker and richer in blood supply and nutrients to prepare for implantation by the fertilized egg.
If the egg is not fertilized, progesterone pregnancy levels drop rapidly, causing most of the endometrium to break down and leaving only a thin layer of tissue.
The broken-down endometrium is shed during your period.
If fertilization takes place, the corpus luteum in the ovary continues to produce progesterone during the first eight weeks of pregnancy.
Once the embryo is implanted in the wall of the uterus, the placenta begins to form.
From the eighth week of pregnancy onwards, the placenta becomes the main source of progesterone.
Normal progesterone levels are essential during pregnancy, particularly in the early stages when progesterone helps stabilize the uterine muscles.
As pregnancy progresses, progesterone acts as a precursor for other hormones essential for normal foetal development.
Progesterone also plays a role in preparing the breasts for milk production, but prevents the release of milk before delivery.
If progesterone pregnancy levels are low, you may have difficulty conceiving or in maintaining a pregnancy.
Low progesterone levels in early pregnancy are a major cause of miscarriage.
In either of these conditions, progesterone supplements may be prescribed to help you become pregnant or to maintain a pregnancy.
If pregnancy occurs, progesterone levels rise further.
In early pregnancy, progesterone maintains the stability of uterine muscles, preventing them from contracting excessively and thereby helping keep the growing embryo in place.
As the foetus grows, it uses maternal progesterone as a precursor for steroid hormones that are essential for normal foetal development.
Progesterone also prevents the release of milk from the breasts during pregnancy. With the onset of labour, progesterone levels drop, allowing the release of milk from the breasts.
Progesterone acts in several other ways within and outside the reproductive system.
As an oestrogen antagonist, it is thought to exert a protective effect against certain uterine and breast cancers.
Progesterone raises core body temperature, acts as a muscle relaxant, and plays a role in maintaining normal bone and thyroid function.
Progesterone is used to control bleeding in women who are not ovulating.
It is also used to maintain early pregnancy, particularly in women who have had repeated miscarriages.
Progesterone cream may reduce symptoms of pre-menstrual syndrome and menopause.
Every month, progesterone levels rise in anticipation of pregnancy, stimulating the thickening of the uterine lining.
If pregnancy does not occur, progesterone (and oestrogen) levels drop-off abruptly and menstruation begins; leading to a renewal of the entire menstrual cycle.
Progesterone is an important precursor hormone for the synthesis of other hormones (oestrogen, testosterone and corticosteroids).
It works to maintain a balance with oestrogen to regulate the menstrual cycle and prevent side effects related to "oestrogen dominance", a condition caused when oestrogen levels are too high relative to the progesterone pregnancy levels.
It also protect against fibrocystic breasts, helps the body rid itself of excess water.
Progesterone helps turn fat into energy, acts as a natural antidepressant, normalizes blood clotting and help normalize blood-sugar levels.
Progesterone may help slow the advance of osteoporosis, helps relieve menopausal symptoms, relieves fatigue, and joint pain.
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