This test measures the level of progesterone to help assess fertility.
What is being tested?
Progesterone is a steroid hormone whose main role is to help prepare a woman’s body for pregnancy. It works in conjunction with several other female hormones. This test measures the level of progesterone in the blood.
On a monthly basis, the hormone estrogen causes the lining of the uterus, the endometrium, to grow and replenish itself, while a surge in luteinizing hormone (LH) leads to the release of an egg from one of two ovaries (ovulation). A corpus luteum then forms in the ovary at the site where the egg was released and begins to produce progesterone. This progesterone, supplemented by small amounts produced by the adrenal glands, stops endometrial growth and readies the uterus for the possible implantation of a fertilized egg.
If fertilization does not occur, the corpus luteum degenerates, progesterone levels drop, and menstrual bleeding begins. If a fertilized egg is implanted in the uterus, the corpus luteum continues to produce progesterone, with the egg forming a trophoblast that produces human chorionic gonadotropin (hCG). After several weeks, the placenta replaces the corpus luteum as the main source of progesterone, producing relatively large amounts of the hormone throughout the rest of a normal pregnancy.
Progesterone is also produced in males but at a much lower level. Its function involves the development of sperm.
How is the test used?
A progesterone test may be used:
- To help recognize and manage some causes of infertility. Since progesterone levels vary throughout the menstrual cycle, multiple (serial) measurements can be used for this purpose.
- To determine whether or not a woman has ovulated (released an egg from an ovary), when ovulation occurred, or to monitor the success of induced ovulation
- In early pregnancy to help diagnose a failing pregnancy (miscarriage) or a pregnancy growing outside the uterus (ectopic), along with human chorionic gonadotropin (hCG) testing
- To monitor a high-risk pregnancy to help evaluate placenta and fetal health
- If a woman is receiving progesterone injections to help support her early pregnancy, to help determine the effectiveness of the replacement treatment
- Along with other tests such as follicle-stimulating hormone (FSH), luteinizing hormone (LH), hCG, and a complete blood count (CBC), to help determine the cause of abnormal uterine bleeding in non-pregnant women
When is it ordered?
Progesterone levels may be measured:
- During an infertility assessment, when a woman is having trouble getting pregnant and her healthcare practitioner wants to verify that she is ovulating normally; the test may be ordered a few times during a woman’s menstrual cycle to evaluate the change in progesterone concentrations.
- When it is necessary to determine when ovulation has occurred and following drug therapy to induce ovulation
- When symptoms, such as abdominal pain and spotting, suggest an ectopic pregnancy or threatened miscarriage
- On a regular basis when a woman requires progesterone replacement therapy to help maintain her pregnancy
- Periodically throughout a high-risk pregnancy to monitor placenta and fetal health
- When a non-pregnant woman is experiencing abnormal uterine bleeding
What does the test result mean?
Interpretation of progesterone test results depends on the reason for testing and requires knowledge of the point at which a woman is in her menstrual cycle or pregnancy. Progesterone levels usually start to increase when an egg is released from the ovary, rise for several days, and then either continue to rise with early pregnancy or fall to initiate menstruation.
If progesterone levels do not rise and fall on a monthly basis, a woman may not be ovulating nor having regular menstrual periods. This may be a cause of infertility.
If levels do not rise normally during an early pregnancy, the pregnancy may be ectopic and/or may be failing. If serial measurements do not show increasing progesterone levels over time, there may be problems with the viability of the placenta and fetus.
Low levels of progesterone may be associated with:
- Ectopic pregnancy
- Fetal death/miscarriage
- Decreased function of ovaries
- Lack of menstruation (amenorrhea)
Increased progesterone levels are seen occasionally with:
- Some ovarian cysts
- Non-viable pregnancies known as molar pregnancies
- A rare form of ovarian cancer
- Overproduction of progesterone by the adrenal glands
- Adrenal cancer
- Congenital adrenal hyperplasia (CAH)
Is there anything else I should know?
Levels of progesterone will be naturally higher during pregnancies that involve multiples (twins, triplets, etc.) than those in which there is only one fetus.
Taking estrogen and progesterone supplements can affect results.
Are men tested for progesterone?
While men have small amounts of progesterone in their blood, progesterone is usually not tested in men, unless specific adrenal diseases are suspected. Progesterone does not have an established role in males.
Is progesterone used as treatment?
Yes. Progesterone (in the synthetic form progestin) is often used in hormone replacement therapy (HRT) for menopausal women who still have their uterus and is used in some contraceptive pills.
If I am menopausal and on hormone replacement therapy (HRT), is there ever a need to monitor my progesterone level?
Sometimes. If you still have your uterus and are having symptoms, such as unexplained uterine bleeding, your health care practitioner may order a progesterone test along with other tests and procedures. If you do not have a uterus (removed during a hysterectomy), your HRT will not include progesterone and it will not need to be checked.