Progesterone is the main representative of one of the two most important groups of female sex hormones - gestagens. The name of progesterone is associated with the most important function of this hormone - procrastination (from Latin pro gestationem - for the maintenance of pregnancy). Where is progesterone produced and how does it work? How is it used in medicine?

Progesteroneis primarily designed to prepare the woman's body, and in particular her reproductive organ, for the fertilization process and the subsequent maintenance of pregnancy.

The effects of progesterone are not limited to the reproductive system, however. This hormone has the ability to bind to receptors distributed in various tissues. For this reason, the effects of progesterone are visible throughout the body.

Structure of progesterone. Where and how is progesterone produced

Progesterone belongs to the group of steroid hormones. The pathway of its formation in the body begins with a cholesterol molecule. The synthesis of all steroid hormones in the human body is a sequence of closely related chemical reactions.

Progesterone can act as an intermediate in the synthesis of other hormones - in just a few reactions it can be converted to, for example, estrogen or testosterone.

Interestingly, the transformation products of this hormone do not have to be only sex hormones. Our body also produces, for example, cortisol and aldosterone.

The sites for the synthesis of progesterone in the human body are:

  • ovaries (specifically the corpus luteum)
  • adrenal glands
  • central nervous system

During pregnancy, progesterone is additionally produced by the placenta. The cells of these organs release progesterone into the blood, where it binds to proteins: albumin or transcortin. In this form, along with blood, it reaches the target tissues in which it is to fulfill its task.

How does it recognize cells in which it should work? Well, it only goes to those that have a special molecule that allows them to receive its signals. This is called the progesterone receptor. The stimulation of this receptor by the progesterone molecule causes specific changes in the functioning of the cell.

As mentioned above,all the reactions of the formation of steroid hormones are interrelated. A similar relationship concerns their effects on receptors.

Progesterone, in addition to binding to its own receptor, can also interact with receptors for other hormones - for example, aldosterone and cortisol.

In turn, thanks to the ability to bind to receptors located in the central nervous system, progesterone can act as a neurotransmitter (a molecule that transmits signals between cells of the nervous system). Many artificial progesterone derivatives, when used as drugs, interact with the receptor for testosterone. The interaction of progesterone with its own receptor is, in turn, enhanced by the action of estrogens.

All these dependencies mean that progesterone can perform a number of different functions, and its action is closely related to the hormonal balance of the entire body.

Progesterone Functions

  • monthly cycle

Changes in the levels of sex hormones during the menstrual cycle are determined by the changing activity of the ovaries during particular phases.

In the follicular phase, the development of the ovarian follicles takes place and the choice of one of them from which the egg will be released during ovulation. During this phase of the cycle, progesterone levels remain low and the hormonal activity of the ovaries is mainly estrogen production. The onset of progesterone release occurs at the beginning of ovulation and is one of the signals that initiate the release of the egg.

After ovulation, the follicle that this cell came from is transformed into a corpus luteum. It is this structure that is responsible for the intense production of progesterone in the luteal phase of the cycle. Its release is strictly controlled by other hormones - the most important role here is played by the luteinizing hormone (LH), produced by the pituitary gland.

When fertilization occurs, beta-hCG (chorionic gonadotropin) is the most important control function until progesterone production is taken over by the placenta.

The most important task of progesterone is to prepare the uterus for embryo implantation. Through it, the mucosa thickens and grows, increases its blood supply and accumulates spare nutrients.

Progesterone also affects the cervical mucus, causing it to thicken and reduce sperm permeability.

If a woman does not become pregnant, the atrophy of the corpus luteum begins approximately 10-11 days after ovulation. Progesterone levels also begin to drop. Excessive mucosathe uterus exfoliates - this is how menstrual bleeding occurs.

  • pregnancy

Progesterone acts as the "caregiver of pregnancy" - it facilitates fertilization, enables the embryo to implant in the uterus and allows the proper maintenance of the pregnancy. During the first 2-3 months of pregnancy, testosterone production takes place in the corpus luteum. This function is then taken over by the bearing.

Progesterone facilitates the implantation of the embryo in a properly prepared uterine mucosa. During pregnancy, it is called temporal and forms the maternal part of the placenta. Its reconstruction allows the embryo to receive nutrients.

Progesterone also allows the gradual growth of the uterine muscle and reduces its contractility, making it possible to report pregnancy.

Together with other hormones, it also has a very important immune function - it allows the mother's immune system to be overregulated so that the fetal tissues are not recognized as foreign.

During pregnancy, a number of significant physiological changes occur in the mother's body through progesterone. Adaptation to this state includes practically all organs.

Progesterone stimulates the respiratory center, which allows to cover the increased demand for oxygen. Thanks to it, smooth muscles throughout the body are also relaxed.

While this is a beneficial phenomenon in the genital tract, in the case of the gastrointestinal tract it leads to a slower peristalsis and a tendency to constipation. Progesterone is also responsible for the tendency to nausea and vomiting early in pregnancy.

In turn, its influence on the thermoregulatory center in the hypothalamus may cause a constant increase in body temperature. The sudden drop in progesterone levels towards the end of pregnancy is probably one of the factors that initiate labor.

  • breast glands

Progesterone stimulates the development of the mammary glands by affecting both the glandular alveoli and the epithelium of the exit ducts. The activity of progesterone in the breast is closely related to the activity of estrogens - they increase the number of progesterone receptors.

During pregnancy, the cooperation of progesterone, estrogens and prolactin enables the adaptation of the breast glands to lactation. Progesterone is also one of the factors responsible for the periodic changes in the structure of the breasts during the menstrual cycle.

The role of progesterone and its receptors in the development and treatment of breast cancer remains the subject of much ongoing research.Some progesterone derivatives, when used as drugs (for example, in hormone replacement therapy), may increase the risk of this cancer.

The presence of progesterone receptors on the surface of breast cancer cells indicates the chance of a good response to hormone therapy. The direct influence of progesterone on the development of breast cancer has not been proven.

Research in this area is quite difficult, because the breast tissue is influenced by many hormones at the same time. Establishing the unambiguous role of progesterone requires many years of scientists' work.

  • central nervous system

One of the most fascinating functions of progesterone is its activity in the central nervous system. Not all of its mechanisms have been fully known.

It is known that progesterone can act as a neurotransmitter - that is, an information transporter between nerve cells. Its action in the areas of regulation of sexual behavior and sex drive seems to be particularly important.

Many scientific studies also point to the neuroprotective role of progesterone. It consists in protecting nerve cells against damage and enhancing their regeneration ability.

The importance of progesterone in other areas of brain function is still being explored: learning, remembering information, addictions, and feeling emotions. The sudden drop in progesterone levels postpartum is now believed to be one of the causes of postpartum depression.

  • metabolic action

Progesterone, through the ability to interact with various receptors throughout the body, has a number of additional functions.

Binding of progesterone to the aldosterone receptor causes an increase in the amount of urine output with the subsequent loss of water and sodium ions.

The effect of progesterone on carbohydrate metabolism includes the increase in the synthesis of glucagon (a hormone that increases blood glucose) and the weakening of the effect of insulin.

Progesterone is also responsible for the perovulatory rise in body temperature. By blocking the 5-alpha-reductase enzyme, progesterone inhibits the production of the active form of testosterone (dihydrotestosterone - DHT). On the other hand, the presence of progesterone receptors in bones enables the regulation of their remodeling.

Normal progesterone levels. Reasons for deficiency and excess of progesterone

  • Normal progesterone levels

The concentration of progesterone in women varies depending on the age and phase of the menstrual cycle.

In the follicular phase it is lowest - usually below 1 ng / ml.

The first increase in concentration takes place in the perovulatory period - then it reaches about 2 ng / ml.

In the luteal phase, progesterone is intensively produced by the corpus luteum. Its concentration reaches its maximum value around day 9 after ovulation. Usually it is in the range of 10-20 ng / ml.

In girls before puberty and in postmenopausal women, the amount of progesterone produced is much lower.

In turn, its concentrations are high during pregnancy - they can range from 11 to 120 ng / ml.

Very low progesterone levels in pregnancy may be associated with the risk of miscarriage. The optimal level of progesterone in men is<1 ng/ml.

  • Excess progesterone

In addition to situations in which progesterone levels are physiologically higher (pregnancy, luteal phase of the cycle), there are also a number of disorders in which there is an overproduction of progesterone.

A common example of such a condition is congenital adrenal hyperplasia, which can occur in both sexes. The disease is characterized by a deficiency of one of the enzymes that allow the adrenal hormones to be produced. Due to the inability to obtain the end products of metabolic reactions, the concentrations of intermediate products - including progesterone - increase.

High levels of progesterone may also be the result of its production by hormonally active tumors (such as the ovaries). Another cause of excess progesterone may be impaired breakdown by the liver.

  • Progesterone deficiency

In medicine, we deal with a deficiency of progesterone much more often. One of the causes of this condition is a failure of the corpus luteum (otherwise known as luteal insufficiency). The corpus luteum then produces too little progesterone, which results in the inability to get pregnant or recurrent miscarriages.

There are also typical menstrual bleeding irregularities and severe PMS symptoms. Low levels of progesterone may also be the result of anovulatory cycles that do not produce a yellow body. Such cycles occur, for example, in the course of polycystic ovary syndrome (PCOS).

Progesterone deficiency may lead to the relative superiority of estrogen's effect on the endometrium. Such a hormonal imbalance can cause endometrial hyperplasia and increase the risk of cancer.

Progesterone as a drug

Progesterone and its artificially obtained derivatives, as well as interacting substanceswith the progesterone receptor, are used in several areas of gynecology and obstetrics. They can be components of contraceptives, drugs used in hormone replacement therapy, and sometimes also as a prophylaxis of premature labor.

  • Miscarriage prophylaxis

In patients whose recurrent miscarriages are caused by a failure of the corpus luteum, progesterone is sometimes used to reduce the risk of losing another pregnancy.

  • Premature delivery

Progesterone is administered vaginally to treat premature uterine contractions. However, the results of clinical trials regarding its administration in the event of a risk of preterm labor are not unequivocal.

  • Non-ovulation cycles

Non-ovulatory cycles are characterized by a lack of release of the egg, which results in the production of the corpus luteum. In such situations, it is recommended to supplement with progesterone, which cannot be naturally produced.

  • Hormone replacement therapy

Progesterone and its derivatives are used in whormone replacement therapy to counterbalance the excessive estrogenic effects that can cause pathological endometrial hyperplasia. This type of protection is not needed for patients who have previously undergone a hysterectomy. The most serious side effect of combined estrogen-gestagen replacement therapy is an increased risk of breast cancer.

  • Endometrial hyperplasia, pathological uterine bleeding, endometriosis

Progesterone is very effective in inhibiting and eliminating benign growth of the uterine mucosa. Its derivatives are used in the treatment of intermenstrual bleeding, heavy and painful periods, as well as endometriosis.

  • Contraception

Artificially obtained derivatives of progesterone are used in preparations that inhibit fertility (alone or in combination with estrogens). They work by inhibiting ovulation, as well as increasing the density of cervical mucus, which prevents sperm penetration.

Substances that have the ability to affect the progesterone receptor are also used as so-called emergency contraception. One example is ulipristal (ulipristal acetate), which delays ovulation for several days. Giving it after sexual intercourse prevents pregnancy.

  • Progesterone test

The last of the worth mentioning uses of progesterone is the so-called progesterone test. Dependsshe was given progesterone not for therapeutic purposes, but as a diagnostic method. This test is to verify the cause of the absence of menstruation. The test consists in the patient taking progesterone for several days, and then discontinuing it.

If there is a menstrual bleeding after discontinuation, the test is positive. It proves the proper production of estrogens by the ovaries and their proper influence on the uterine mucosa. In this case, the amenorrhea is probably caused by anovulatory cycles and secondary luteal failure.

A negative test result is the absence of menstrual bleeding after progesterone discontinuation. The reasons for this can be various: estrogen deficiency, disorders of the hypothalamic-pituitary-ovaries endocrine axis, lack of responsiveness of the uterine mucosa to changing hormone levels, or congenital defects of the reproductive organ preventing menstruation.

About the authorKrzysztof BialaziteA medical student at Collegium Medicum in Krakow, slowly entering the world of constant challenges of the doctor's work. She is particularly interested in gynecology and obstetrics, paediatrics and lifestyle medicine. A lover of foreign languages, travel and mountain hiking.

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Pregnancy