Most commonly, progesterone is requested during the investigation of infertility, to look for the presence of ovulation. It may also be used to help diagnose an ectopic or failing pregnancy or in the investigation of abnormal uterine bleeding, however these are not indications recommended by NICE (National Institute for Health and Care Excellence).
At specific times during a woman’s menstrual cycle (period) to determine whether/when she is ovulating.
A blood sample taken from a vein in your arm
This test measures the concentration of progesterone in the blood. Progesterone is a hormone whose main role is to help prepare and maintain a woman’s endometerium (lining of the womb/uterus) for pregnancy; it works together with several other female hormones.
On a monthly basis, the uterus and ovaries undergo a cyclical change under the control of hormones. The first half of the cycle is characterised by the hormone oestrogen, produced by the ovaries, causing the endometrium to grow and replenish itself.
Increasing oestrogen levels cause a surge in luteinising hormone (LH) mid-cycle leading to the release of an egg from one of the two ovaries. In the second half of the cycle the corpus luteum (a small yellow mass of cells) forms in the ovary at the site where the egg was released and begins to produce progesterone. This progesterone stops endometrial growth and prepares the uterus for the possible implantation of a fertilised egg. If fertilisation does not occur, the corpus luteum degenerates, progesterone concentrations fall, and the endometrial lining is shed (menstruation).
Progesterone levels (produced from the corpus luteum) peak 7 days prior to the onset of menses. If a menstrual cycles is regular and conforms to a standard 28 day length, progesterone concentrations will normally peak on approximately day 21 of the cycle (with day 1 being the first day of menstruation). Therefore, when assessing for ovulation, progesterone should be measured at day 21 of the cycle or 7 days prior to the expected onset of menses. If a woman has an irregular or prolonged cycle then progesterone can be measured on a weekly basis until the onset of menses.
If an egg is fertilised following ovulation, and becomes implanted in the uterus, the corpus luteum continues to produce progesterone. 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.
How is it used?
Since progesterone concentrations vary predictably throughout the menstrual cycle, measurements can be used to help diagnose infertility problems. Progesterone measurements can determine if and whena woman has ovulated (released an egg from the ovary).
In early pregnancy, progesterone measurements may sometimes be used to help diagnose an ectopic pregnancy or failing pregnancy (one leading to miscarriage). NICE however recommends the use of ultrasound scanning along with human chorionic gonadotrophin (hCG) testing in the diagnosis of early pregnancy problems rather than measuring progesterone.
When is it requested?
Progesterone concentrations may be measured:
- As part of an infertility assessment, when a woman is having trouble getting pregnant and the doctor wants to verify that she is ovulating normally. The timing of sampling will depend on the lenght of the menstrual cycle.
- To determine if and when ovulation has occurred following drug therapy to induce ovulation, as part of fertility treatment.
What does the test result mean?
Interpretation of progesterone test results requires accurate knowledge of where a woman is in her menstrual cycle or pregnancy. Progesterone concentrations in the blood usually start to rise when an egg is released from the ovary, continue to rise for several days, and then either continue to rise with early pregnancy or fall to start menstruation.
If progesterone concentrations do not rise and fall on a monthly basis, a woman may not be ovulating or having menstrual periods. If concentrations do not rise normally during an early pregnancy, the pregnancy may be ectopic and/or may be failing.
Levels of progesterone will be naturally higher during pregnancies that involve multiples (twins, triplets, etc.) than those in which there is only one fetus.
Is there anything else I should know?
Are men tested for progesterone?
Are there other uses for progesterone?
Yes. Progesterone (in the synthetic form progestogen) is used in hormone replacement therapy (HRT) for menopausal women who still have a uterus (not removed by hysterectomy) . For more information, read the NHS Choices pages on HRT. Progesterone is also 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?