What is progesterone?

The ovaries are an organ of great importance to the female body. They are located on either side of the uterus and each is made up of two parts - cortical and medullary. The ovaries change in size with age and are responsible for producing, among other things:

oestrogens;
androgens;
relaxins;
progesterone.

Estrogens and androgens are responsible for secondary and tertiary sexual characteristics. They have a significant impact on our appearance and well-being.

Progesterone is a female sex hormone of steroidal structure. It is produced by the ovaries, adrenal cortex and placenta, belongs to a group of hormones called gestagens. During the menstrual cycle, during ovulation, the remnants of the ovarian follicle from which the ovum has been released form a structure called the corpus luteum. It releases mainly progesterone and in addition also, amongst others, oestrogens and androgens. During this time, progesterone prepares the body for pregnancy. If conception does not occur, the corpus luteum disappears and the whole cycle starts from the beginning. Progesterone levels therefore drop significantly after ovulation.

What if, however, fertilisation occurs? Then progesterone stimulates congestion, distension and relaxation of the uterine muscle, increases the concentration of glycogen in the tissues (sugar storage) and enhances secretory metabolism in the uterine mucosa. As a result, the embryo is implanted in the uterine cavity and is nourished.

Progesterone standards in pregnancy

During pregnancy, progesterone helps to maintain the transformation of the endometrium. In the early stages, the hormone is produced all the time by the corpus luteum, as it is necessary to maintain the pregnancy. In the next stage, it is the placenta that takes over the production of progesterone. This occurs around the 8th to 12th week of pregnancy.

Throughout pregnancy, progesterone plays a very important role in the fetal development cycle:

stimulates the growth of breast tissue in the mother-to-be;
prevents lactation;
relaxes the muscles of the pelvic wall, preparing them for childbirth.

The level of the hormone rises in a woman's body throughout pregnancy, until termination. The aforementioned corpus luteum in the ovaries is mainly responsible for its production. However, it is also produced by the ovaries, the adrenal glands and the placenta.

What are the progesterone standards in pregnancy?

1st trimester: 11.0-44.3 ng/ml,
2nd trimester: 25.4-83.3 ng/ml,
3rd trimester: 58.7-214 ng/ml.

In other women, progesterone norms should be at:

Follicular phase: 0.057-0.893 ng/ml,
Ovulatory phase: 0.121-12.0 ng/ml,
Luteal phase: 1.83-23.9 ng/ml,
after menopause: <0.05-0.126 ng/ml.

The reference level of progesterone depends on various factors such as, for example, age, sex and the method of determination.

Adequate progesterone levels. When to check it?

Too high or too low progesterone should always be a reason for appropriate tests. When is it most common for a doctor to order a blood progesterone test?

when the presence of tumours producing this hormone is suspected;
during pregnancy - this helps to monitor the pregnancy, the function of the corpus luteum and the placenta, especially if there is a risk of miscarriage or premature birth;
when confirming ovulation;
for irregular menstrual periods;
for genital bleeding.

What do progesterone test results say about pregnancy?

Regarding progesterone standards in pregnancy, its levels can be particularly high in multiple pregnancies. How does this affect the woman's body? Usually, it does not cause negative effects. However, side effects can be:

mood swings;
runny nose and blocked nose;
painful, very sensitive breasts;
body fatigue and the need for frequent rest.

What does low progesterone in pregnancy mean?

By far the bigger problem is progesterone levels too low. Why? Because it increases the risk of miscarriage and can also indicate an ectopic pregnancy. This is because the membrane of the uterus is not ready to receive the embryo and is therefore thin and not well supplied with blood. This prevents the embryo from developing properly. There are, of course, ways of restoring its proper level. Your doctor may prescribe a synthetic form of the hormone: orally, vaginally, intramuscularly or subcutaneously as injections. Dydrogesterones (active metabolites of progesterone) are given orally, in the traditional tablet form.

Prophylactic progesterone intake reduces the possibility of preterm birth in both the group of women with singleton pregnancies and those with high-risk pregnancies. Such measures significantly reduce the rate of preterm birth. Its use is also justified in women who have already given birth several times prematurely or have a history of miscarriage [1]. However, we should remember that everything depends on the recommendations of the attending physician and his assessment of the condition and course of the pregnancy.

Bibliography:

https://www.mjakmama24.pl/ciaza/przebieg-ciazy/progesteron-w-ciazy-poziom-progesteronu-czym-grozi-niedobor-progesteronu-aa-SUFk-naYg-NMB2.html#niedobor-progesteronu-w-ciazy

Authorisation of content:

Blanka Malczewska, M.D. - specialist gynaecologist-obstetrician from the InviMed Clinic in Gdynia