Progesterone: Function, Symptoms and more

Where is progesterone produced?

Progesterone is mainly produced in the ovaries in the so-called corpus luteum and is therefore also called corpus luteum hormone. The corpus luteum matures after ovulation in the second half of the menstrual cycle and progesterone levels therefore change during the menstrual cycle: In the first half of the cycle (during the follicular phase, so from menstruation to ovulation) the hormone estradiol, which belongs to the estrogens, initially predominates. The concentration of progesterone in the blood is low in this phase. In contrast, it increases in the second half of the cycle, the luteal phase. Estradiol and progesterone interact to control the build-up of the uterine lining in preparation for a possible pregnancy.

At the end of the luteal phase the concentration of progesterone decreases again. As a result, the uterine lining is shed and menstrual bleeding begins. If pregnancy occurs, however, the progesterone concentration continues to rise. After some time, it is mainly the placenta that produces progesterone.

What does progesterone do?

To put it simple, the main function of progesterone is to make you pregnant and to keep you pregnant. Initially, Progesterone primarily affects the uterus as it converts the lining of the uterus in the luteal phase, which affects cells, vessels, glands and cells of the uterine lining. Through this transformation, it is well prepared for the implantation of the fertilized egg and later supplies the embryo with nutrients. During pregnancy, progesterone prevents the development of further eggs and the onset of menstruation. Additionally, Progesterone also stimulates the growth of the mammary glands in your breasts for the release of milk.

Other functions of Progesterone

Bone maintenance: To maintain strong bones, the bone substance is built up and broken down in a controlled manner. In addition to the estrogens, progesterone also strengthens the bones: While estrogens inhibit the breakdown of bone substance, progesterone promotes the formation of new bone substances.

Skin & Hair: Progesterone reduces increased concentrations of male sex hormones in women. As a result, the skin texture may become more refined and hair growth improved.

Increased metabolic rate: Furthermore, progesterone stimulates your metabolism. This increases appetite and also your the body temperature increases after ovulation (approx. 0.5 degrees Celsius).

Progesterone acts on the nervous system: In addition, progesterone has positive effects on the nervous system. It relieves anxiety, promotes sleep, relaxes and calms the nervous system. For many women, a lack of progesterone is associated with anxiety, sleep disorders and mood swings.

Progesterone protects your uterus and breasts: Progesterone prevents the stimulating effect of estrogens on the uterine tissue and therefore reduces the risk of adenoids of the uterine lining and protects against uterine cancer. It can also have a protective effect on breasts.

Progesterone throughout your cycle

The progesterone value changes throughout the cycle. In particular, the luteinizing hormone (LH) from the pituitary gland plays an important role here. Initially, the progesterone concentration is low in the first half of the cycle (follicular phase). However, after LH triggers ovulation, the corpus luteum is formed in the second half of the cycle (luteal phase) which releases progesterone. The progesterone level rises accordingly and towards the end of the luteal phase, progesterone levels drop again and menstruation begins.

Low progesterone concentrations are present in the first half of the cycle and after menopause (postmenopause). In contrast, the progesterone level is high in the luteal phase. If a pregnancy occurs, the progesterone concentration continues to rise. In the second half of pregnancy the placenta takes over the production of progesterone: It then produces up to 10 times more progesterone than the corpus luteum produces in the luteal phase. This shows that a high progesterone level is obviously necessary to support a pregnancy.

Causes and consequences of progesterone deficiency

In case of progesterone deficiency, the corpus luteum produces too little progesterone. There are several names for this condition:

**-**Corpus luteum weakness,

**-**Corpus luteum insufficiency,

- Luteal phase defect (abbreviated LPD) or

- Luteal phase insufficiency

Causes are, for example, underdeveloped ovaries, cycles without ovulation or disorders of ovulation. A short luteal phase of less than 10 days, for example, is an indication of insufficient progesterone levels. This often results in cycle disorders and a desired pregnancy is difficult to achieve or does not occur at all. In addition, low progesterone levels increase the risk of miscarriage in early pregnancy. Experts therefore recommend that in these cases progesterone should be given to support the pregnancy.

Little progesterone in menopause

A low progesterone concentration is not always associated with a disorder. During menopause, the progesterone level drops naturally and then remains at about 0.2 ng/ml. This is sometimes the cause of typical menopausal symptoms, such as sleep disturbances and mood swings.

Treatment with progesterone

During the fertile phase of a woman's life, the range of applications of progesterone is wide. Here progesterone counteracts a disturbed menstrual cycle if this is due to a lack of progesterone. Furthermore, progesterone is used to support the luteal phase in the case of in vitro fertilization. The application is preferably vaginal. In certain high-risk pregnancies, progesterone can prevent miscarriage and premature birth.

Progesterone is also used as part of hormone therapy for women during and after the menopause. Here it protects the lining of the uterus from estrogen-induced adenoids when an estrogen supplement is taken and it can also be used to relieve menopausal symptoms.

Progesterone and corpus luteum insufficiency

Women with corpus luteum insufficiency often have an irregular menstrual cycle. Progesterone can help to counteract these irregularities. An insufficiency of the corpus luteum also regularly occurs during so-called ovarian stimulation in artificial insemination. Here, Progesterone is the standard therapy, which is because if progesterone levels are too low, the egg cell does not implant. If the therapy is continued up to the 12th week of pregnancy, the risk of early miscarriages due to progesterone deficiency is minimized.

Does Progesterone help with repeated miscarriages?

In some women with repeated miscarriages, also called habitual abortions, progesterone administration is useful. Studies have shown that progesterone reduces the risk of further miscarriages. However, progesterone does not help every woman. For this reason, the benefits of progesterone must be weighed up against the risks for every woman who wishes to have children.

Progesterone is also used to support pregnancy in women with a prematurely shortened cervix. Normally the cervix is shortened at the end of pregnancy to induce delivery. However, if the cervix is shortened prematurely, premature birth may be imminent. Several studies show that the administration of progesterone in the second and third trimesters of pregnancy results in fewer premature births.

Progesterone for menopausal symptoms

During menopause, the woman's body produces less estrogens and gestagens. This is the cause of irritating menopausal symptoms such as hot flashes and sleep disturbances. The symptoms considerably restrict the quality of life of many patients and hormone replacement therapy (HRT) can be used to counteract these symptoms. This involves replacing the hormones that the body no longer produces. HRT involves the administration of estrogens in particular, often in combination with a gestagen. Natural progesterone plays an important role here, as it has several advantages over synthetic gestagens.

How is progesterone administered?

There are many different forms and ways of taking progesterone. Progesterone is used in the form of capsules, tablets, gel or as a syringe for injection. Just as varied is the method of application: progesterone preparations can be swallowed or inserted vaginally. Progesterone can also be injected under the skin or into the muscle. Pharmacies also make progesterone creams for application to the skin and dispense them on prescription. The effectiveness varies depending on the method of administration.

What are possible side effects of progesterone?

Progesterone is generally well tolerated. However, studies have shown, that users can experience the following side effects:

- Drowsiness,

- temporary dizziness,

- Feeling full, stomach ache

and

- Breast tenderness

In most studies with progesterone no serious side effects occurred but nevertheless, experts recommend weighing the benefits against the risks of progesterone therapy.

Sources

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Romero R, Conde-Agudelo A, Da Fonseca E, et al. Vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix: a meta-analysis of individual patient data. American journal of obstetrics and gynecology. 2018;218(2):161-180.

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