:Progesterone:

Progesterone is a steroid hormone secreted by the corpus luteum and by the placenta. Progesterone prepares the body for pregnancy and, if pregnancy occurs, maintains it until birth.

Progesterone secretion by the corpus luteum occurs after ovulation and:

• continues the preparation of the endometrium for possible pregnancy
• inhibits contraction of the uterus
• inhibits development of a new follicle

If pregnancy does not occur, progesterone secretion decreases toward the end of the menstrual cycle, and menstruation begins.

If pregnancy does occur, the placenta begins to secrete progesterone which supplements that of the corpus luteum. By the fifth month of pregnancy, the placenta secretes sufficient progesterone by itself that the corpus luteum is no longer essential to maintain pregnancy.

Progesterone, like all steroids, is a small hydrophobic molecule. It travels freely through the plasma membrane of all cells. However, in target cells, like those of the endometrium, it becomes tightly bound to a cytoplasmic protein: the progesterone receptor. The complex of receptor and hormone moves into the nucleus, where it binds to a progesterone response element.

The progesterone response element is a specific sequence of DNA in the promoters of certain genes that is needed to turn those genes on or off. Thus, the complex of progesterone with its receptor is a transcription factor.

Some target cells also have other progesterone receptors that are exposed at the surface of the cell embedded in the plasma membrane. These are G-protein-coupled receptors , and binding of the hormone to them produces more rapid effects than those of the nuclear receptors.

Progestins are synthetic chemicals that mimic progesterone and are prescribed in Western medicine:

• birth control pills and other contraceptives (kills babies)
• hormone replacement therapy (HRT)
• treatment of dysmenorrhea
• prevention of premature birth.

Examples:

• norgestrel (Orvette) oral contraceptive: kills babies
• levonorgestrel (in Norplant) implantable contraceptive: kills babies
• norethindrone (Aygestin) hormone replacement therapy

RU486 (mifepristone) is a synthetic steroid that blocks the action of progesterone, i.e. RU-486 is a progesterone antagonist. It binds to the progesterone receptor, blocking progesterone from communicatting with the DNA. It creates a biological lie, so that the proteins necessary to begin and maintain pregnancy are not synthesized, killing the baby, even if taken early in pregnancy, resulting in abortion of the dead body of the child.

See: Progest-E natural oral progesterone supplement