Back Blood-tests Explained

Progesterone

At a Glance

Why Get Tested?

To help determine the cause of infertility, track ovulation, help diagnose an ectopic or failing pregnancy, monitor the health of a pregnancy, monitor progesterone replacement therapy, or help diagnose the cause of abnormal uterine bleeding

When to Get Tested?

At specific times during a woman's menstrual cycle to determine whether/when she is ovulating; during early pregnancy when symptoms suggest an ectopic or failing pregnancy; throughout pregnancy to help determine placenta and fetal health; periodically when a person is receiving progesterone replacement therapy; when a woman has abnormal uterine bleeding

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

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. 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 sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed. The patient's last menstrual period and trimester of pregnancy should be noted.

The Test

How is it used?
When is it ordered?
What does the test result mean?
Is there anything else I should know?

How is it 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, when ovulation occurred, or to monitor the success of induced ovulation
In early pregnancy to help diagnose an ectopic or failing pregnancy, 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 an FSH, LH, hCG, thyroid tests, clotting tests, 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 are measured:

During an infertility assessment, when a woman is having trouble getting pregnant and her health care provider 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 elevate 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.

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)

Low levels of progesterone may be associated with:

Toxemia late in pregnancy
Decreased function of ovaries
Lack of menstruation (amenorrhea)
Ectopic pregnancy
Fetal death/miscarriage

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.

Men will also have small amounts of progesterone in their blood.

A limited number of laboratories can perform progesterone testing on saliva.

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