Progesterone hormone: functions, normal values and medications

Progesterone is a female sex hormone that has important functions in the female menstrual cycle and pregnancy.

Progesterone is mainly synthesized by the ovaries and placenta during pregnancy, although it is also produced by the adrenal glands and the liver in smaller quantities.

In assisted reproduction, progesterone is known to be the active ingredient of some drugs used in treatments, especially for being the main cause of some annoying symptoms.

What is progesterone?

Progesterone is a steroid hormone belonging to the progestogen group, i.e., the hormones responsible for maintaining pregnancy. For this reason, progesterone is also known as the pregnancy hormone.

Its production begins once a woman has reached puberty, with the first menstruation and the onset of menstrual cycles. This is why progesterone is a sex hormone that also contributes to the appearance and development of female secondary sexual characteristics.

Progesterone production by the corpus luteum

Specifically, progesterone is synthesized by the woman's ovaries after ovulation. Once the egg is expelled, the ovarian follicle becomes a corpus luteum that secretes progesterone throughout the luteal phase of the menstrual cycle until menstruation arrives.

What is progesterone used for?

The hormone progesterone has multiple functions in the human body, both in women and men.

However, in this section, we will focus on the functions of progesterone in the female reproductive system.

As mentioned above, progesterone levels increase during the second half of the menstrual cycle, just after ovulation. However, towards the end of the menstrual cycle, these levels begin to decrease or are maintained depending on whether or not there has been implantation of the embryo in the uterus.

In the following, we will discuss these two assumptions.

In a woman's menstrual cycle

Progesterone is synthesized in the luteal phase of the cycle with a clear objective: to make the endometrium receptive so that the embryo can nest in it and initiate a pregnancy.

If this does not occur, progesterone levels decrease during the fourth week of the menstrual cycle and this causes shedding of the endometrium in the form of menstruation. That is, as there has been no implantation or pregnancy, this endometrium has to be eliminated so that it can regenerate again in the next menstrual cycle.

In addition, progesterone also causes the mammary glands to enlarge in the days leading up to menstruation.

In pregnancy

On the other hand, if the fertilized embryo has been implanted in the endometrium, the corpus luteum or yellow body of the ovary will continue to produce progesterone until about week 10 of pregnancy. The placenta will then be responsible for the secretion of progesterone until the end of gestation.

Its function is to maintain the uterine tissue in good condition throughout pregnancy. As a result, progesterone levels progressively increase month by month until they finally decline and labor is triggered.

Functions of progesterone in women

Another function of progesterone during gestation is to thicken the cervical mucus so that it becomes impermeable to sperm.

In addition, progesterone is also responsible for breast enlargement during pregnancy and for preparing the mammary glands to secrete breast milk after giving birth.

Serum progesterone

Serum progesterone is a test that measures the level of this hormone in the blood.

This test is performed to detect any disturbance in the normal progesterone levels, which could lead to fertility problems, threatened miscarriage, etc.

The progesterone test is also used to find out if the woman has ovulated. In this particular case, the blood test should be done on day 21 of the menstrual cycle.

In the following sections, we will discuss what altered progesterone levels may mean.

High progesterone

If after the blood test, the results show a higher than normal progesterone value, this could be indicative of:

• Pregnancy
• Ovarian cyst
• Molar pregnancy.
• Ovarian cancer
• Adrenal cancer
• Congenital adrenal hyperplasia

When is progesterone high?

However, it is advisable to repeat the test, as well as to perform other complementary tests to obtain a more accurate diagnosis.

Low progesterone

Conversely, if progesterone levels are below baseline values, this could be indicative of:

• Anovulation (no ovulation)
• Threat of abortion
• Ectopic pregnancy
• Intrauterine fetal death

When is progesterone low?

Obviously, for this test to indicate possible problems in pregnancy, pregnancy must have been confirmed beforehand, for example by means of a pregnancy test.

Drugs with progesterone

On some occasions, it is necessary to administer progesterone artificially in order to treat some menstrual alterations, prevent risk situations or support the early stages of pregnancy.

Medications that include progesterone as an active ingredient have different presentations:

In oral tablets

this is the case of contraceptives that include progesterone to inhibit ovulation so that there is no risk of unwanted pregnancy. In addition, contraceptives that only include progesterone exclusively are known as mini-pills. These drugs are also used for hormone replacement therapy (HRT) in women who have reached menopause or to treat some hormonal imbalances along with estrogens.

In vaginal ovules

are micronized progesterone suppositories that are inserted through the vagina and are usually prescribed for luteal phase support infertility treatments, such as artificial insemination (AI) or in vitro fertilization (IVF). They are also used when there is a threat of miscarriage or when there is a risk of premature delivery. Utrogestan and Progeffik are the most popular progesterone drugs and both have the same price.

Vaginal gel

its form of administration is simpler than in the previous case and usually has the same indication. One of these drugs is Crinone.

Progesterone medications

In injections

for women who have a major progesterone deficiency or who do not assimilate the eggs or gel. They are subcutaneous or intramuscular injections that must be applied daily. One of these drugs is Prolutex and it has a much higher price than the previous formats.

FAQs from users

What is progesterone used for after IVF?

In vitro fertilization (IVF) is a treatment in which embryos are generated in the laboratory from the gametes of the future parents or from anonymous donors. These embryos are then placed in the woman's uterus by embryo transfer.

In order for these embryos to implant in the endometrium, the endometrium must have the same characteristics as it would have had if fertilization had taken place in the uterus and not in the laboratory.

This implies that the endometrium must be exposed to the same hormonal variations as in a natural cycle. For this purpose, progesterone administered exogenously by means of vaginal or oral ovules is used.

Can I have anovulation due to lack of progesterone?

No. The lack of progesterone is conditioned by the lack of ovulation, not the other way around.
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Why do some women take progesterone after embryo transfer and others do not?

In a normal cycle, after ovulation, progesterone begins to rise so that the endometrial tissue can be modified to allow implantation and the development of the eventual embryo. When we perform an embryo transfer, what we need is to reproduce this situation so that the embryo can implant.

Normally, the progesterone treatment starts a few days before the embryo transfer. In case of transfer in the same cycle as the follicular puncture, it starts the same day of the puncture, otherwise, it varies according to the stage of embryo development.

In case of transfer in a natural cycle (when no hormonal treatment is given to prepare the endometrium), progesterone is started on the same day of the transfer, but it is very unlikely that progesterone does not have to be taken after the embryo transfer because it is always preferred to support the luteal phase with exogenous progesterone.

Is it possible that my progesterone is high because I have only had eggs removed from one ovary?

No. The fact that only eggs are obtained from one ovary does not determine whether the amount of progesterone in the blood is higher or lower.
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Do men also produce progesterone?

Yes, but in much lower amounts than women. Progesterone in the male sex is secreted by the adrenal glands and testes.

One of its functions in the male body is to regulate glucose levels and prevent prostate hyperplasia. In addition, progesterone is the precursor of testosterone, the male sex hormone par excellence.

Why don't I get my period after stopping progesterone?

If progesterone is taken for a long time, amenorrhoea, i.e. absence of menstruation due to atrophy of the endometrium, may occur.
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What foods can I take to improve progesterone?

Through nutrition, it is possible to optimize the production of progesterone by the corpus luteum.

In general, foods that improve blood circulation are recommended, such as those rich in L-arginine and L-citrulline (watermelon, salmon, peas, green beans, chia seeds, sesame, nuts, etc.), those that stimulate the production of nitric oxide (beets, strawberries, carrots, spinach, chard, broccoli, etc.) and others that improve the health of the vascular wall (chocolate, garlic, onion, etc.).

It is also essential to maintain good levels of some micronutrients such as omega-3, zinc, vitamin B6 and antioxidants. To this end, it is recommended to include the following foods in the diet: sardines, salmon, mackerel, shellfish (rich in omega-3); whole grains, legumes, nuts and liver (rich in vitamin B6); pumpkin seeds, shellfish and white meats (rich in zinc); vegetables and fruits (rich in antioxidants).

Does the use of progesterone cause threatened miscarriage?

No, quite the opposite. Progesterone is sometimes prescribed to prevent possible miscarriages. This hormone helps to prepare the endometrium to be receptive and, therefore, to promote embryo implantation.

Progesterone also helps to keep the uterus in the ideal conditions for pregnancy to develop normally.

Recommended readings

Throughout the article, we have discussed the menstrual cycle, its phases, and the hormones involved in it. If you would like more information about this, we encourage you to continue reading here: The menstrual cycle: what happens in each of its phases?

You can also find out what are the normal values of hormones in women in the following article: Hormonal analysis in women.

Finally, you can find information about sex hormones and what their functions are in the following post: Male and female sex hormones.