Progesterone Hormone Definition - What Is Progesterone ?

What is progesterone?

Progesterone is a sex hormone that by the corpus luteum (yellow body in the ovary) in the second phase (luteal phase) of the menstrual cycle, and in greater quantities during pregnancy is produced by the placenta. Progesterone is also produced in the adrenal cortex during the synthesis of steroid hormones in both women and men. Significant amounts of progesterone, however, are found only in women.

Another name for this hormone is corpus luteumhormoon.


Progesterone (CAS No. 57-83-0) is synonymous pregn-4-en-3,20-dione and its molecular formula C21H30 O2. The molecule is a steroid, and is therefore composed of four connected carbon rings. The ketone and aldehyde-containing components, as well as two methyl groups. The molecule is hydrophobic (water repellent) in that it has no highly polar functional groups.


Progesterone is formed from pregnenolone, which is a derivative of cholesterol. The 3-hydroxyl group is transformed into a ketone group in a first step. In the second step, the double bond of the C5 is moved to the C4 atom.

Progesterone is the precursor of all steroid hormones, such as cortisol, aldosterone, testosterone, estradiol, estriol and estrone. It is also widely used as finished and semi-finished product produced industrially.

Other progesterone is converted by metabolism in pregnanediol and is eventually excreted in the urine.


After ovulation, in the luteal phase of the menstrual cycle, stimulates the luteinizing hormone (LH) together with follicle stimulating hormone (FSH), the production of progesterone by the corpus luteum in the ovary. Under the influence of progesterone, the endometrium is prepared for the implantation of the fertilized ovum. If pregnancy fails, the production of progesterone by the corpus luteum gradually come down to, ultimately resulting in a menstrual bleeding.

 is a sex hormone that by the corpus luteum  Progesterone Hormone Definition - What Is Progesterone ?

If pregnancy occurs takes the pregnancy hormone hCG stimulation of progesterone on and there will be no menstrual bleeding occur. The hCG, which is produced by the developing embryo in minimal quantities, ensures that the corpus luteum remains and continues to produce progesterone, until the placenta takes over the production of progesterone.

Progesterone also ensures that the mucus in the cervix so sperm changed it bothered to enter the uterus. Progesterone also inhibits ovulation by inhibiting the release of LH by the pituitary gland and thereby prevents the possibility of a late fertilization of a possible second egg. Both features are designed to reduce the risk of multiple births.

Progesterone also reduces the stimulation of the muscle around the uterus, so that a repulsive reaction against the foreign embryo is suppressed.

During pregnancy promotes progesterone along with estrogen hormones, prolactin, cortisol, insulin and thyroid hormones increase the mammary glands (breasts in women).

Progesterone Determination

Progesterone may be measured in blood on a clinical chemistry laboratory. Indications for the measurement of progesterone in blood are as follows:
  • Determine if ovulation has taken place there: the amount of progesterone in the blood is monitored during the menstrual cycle. When the progesterone concentration in the second half of the menstrual cycle (luteal phase), exceeds a certain threshold value, it is thereby shown that there has been an ovulation (ovulation) occurred. When progesterone does not rise above a certain threshold, it can mean that no ovulation and / or menstruation occurs.
  • Monitoring the course of the pregnancy: during early pregnancy increase the progesterone and hCG concentration according to a certain fixed pattern. If not enough progesterone increases during early pregnancy, which may indicate an ectopic pregnancy or a miscarriage.

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