Progesterone is a hormone found in human beings, and is derived from cholesterol. In women, Progesterone is helps maintain a normal menstrual cycle and plays an important role during pregnancy. In both women and men, Progesterone is a precursor of testosterone and estrogen. Progesterone is primarily produced by the adrenal glands. Smaller amounts are also produced in the ovaries following ovulation, by the brain, and by the placenta during pregnancy.
Progesterone levels are normally low in children, men and post-menopausal women. In pre-menopausal women, Progesterone levels fluctuate during the menstrual period. They are low before ovulation, and rise following ovulation. Progesterone plays an important role in preparing the endometrium, or tissue lining the uterus, for implantation of the fertilized egg. If pregnancy does not occur, Progesterone levels drop, the endometrium is shed through menstruation, and the menstrual cycle starts over.
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 fetus grows, it uses maternal Progesterone as a precursor for steroid hormones that are essential for normal fetal development. Progesterone also prevents the release of milk from the breasts during pregnancy. With the onset of labor, 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 estrogen 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.
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