What is progesterone
Progesterone is a steroid hormone initially secreted after ovulation by the corpus luteum, an area in the ovary which develops after ovulation. Prior to ovulation, progesterone levels are very low. They increase right after ovulation and reach levels above 10 ng/ml usually by 5-7 days after ovulation. If you are not pregnant, progesterone levels usually decrease around the time of the next menstrual period bleeding.
What is a normal progesterone level
Before ovulation, progesterone is well below 10nd/ml and after ovulation it is well above 10ng/ml. The time right after ovulation until the next menstrual period is called the “corpus luteum phase”or the “luteal phase.” During the luteal phase the fertilized egg travels through the fallopian tube into the uterus where it implants usually 6-12 days after fertilization. The normal luteal phase lasts on average 14 days, and it can be anywhere from 12 to 17 days long.
Progesterone prepares the endometrium, the lining of the uterus, for implantation and a possible pregnancy, it prevents contractions of the uterus and the development of a new follicle, and during pregnancy it is being produced by the placenta and maintains the pregnancy until birth.
Why measure progesterone levels
Measuring progesterone levels can determine if you ovulated or not and whether a pregnancy is viablke or not or if there is a normal pregnancy or not. Low progesterone levels may be a problem. When you ovulate there is an area in the ovary called "corpus luteum" which is responsible for the production of progesterone. Low progestone levels below 10 ng/ml usually mean that ovulation has likely not happened or you tested too early, less than a week after ovulation.
Every month when ovulation occurs, the area in the ovary from where ovulation occurs develops into the corpus luteum or the "yellow body". The corpus luteum in the ovarya secretes the hormone called Progesterone which plays important roles in the menstrual cycle and in maintaining the early stages of pregnancy. Progesterone levels rise in the blood after ovulation and progesterone blood level in a normal pregnancy can be up to 10 times higher than when you are not pregnant. However, it's impossible to diagnose a pregnancy from progesterone levels. Only the pregnancy hormone hCG Human Chorionic Gonadotropin can make a pregnancy diagnosis.
As soon as the the egg is fertilized, the progesterone hormone stimulates the growth of blood vessels that supply the lining of the womb (endometrium) and stimulates glands in the endometrium to secrete nutrients that nourish the early embryo. Progesterone is responsible to get the tissue lining of the uterus ready to allow the fertilized egg to implant and helps to maintain the endometrium throughout pregnancy.
Can pregnancy be diagnosed from a progesterone level alone?
Progesterone levels normally rise during the first 36-38 weeks of the pregnany, then fall towrads the due date. Pregnancy cannot be diagnosed in and by itself from progesterone levels. Only the presence of hCG the pregnancy hormone hCG either in the blood or urine diagnoses a pregnancy. Progesterone levels or elevated progesterone levels alone cannot diagnose a pregnancy. Progesterone cream cannot be used after ovulation to improve fertility or pregnancy outcome.
Diagnosing ovulation from progesterone levels
Progesterone levels are usually drawn about a week after presumed ovulation because they reach peak levels at that time. Drawing the blood too early may give a false negagtive test results. A false negative progesterone level reult means that you did ovulate but the blood was drawn too early and therefore the ;progesterone level was falesly low. After ovulation, progesterone is produced increasingly from the corpus luteum and the progesterone levels gradually rises from a baseline of 1.5 to 3 ng/mL by the first day after ovulation. Levels then continue to rise until it reaches a peak 7 days after ovulation reaching levels of approximately 10-20 ng/mL. Levels of progesterone can vary depending on the timing of the blood draw, and even on the same day they can be very different.
Normal progesterone levels test results
Progesterone levels are only averages and they can change based on many variables. For example, the timing of the cycle, whether you ovulate or not, which lab tested them, whether blood is taken after you eat or before, and whether it's in the morning or afternoon, can all affect the outcome of a progesterone level test.
- Women at the beginning of their menstrual cycle: 1 ng/mL or under
- Before you ovulate, progesterone levels are usually below 10 ng/ml
- In the middle of the second half of the cycle, midcycle, about 7-10 days after ovulation, progesterone levels are usually above 8-10 ng/ml.
- Women in the middle of their menstrual cycle: 5 to 20 ng/mL
- First trimester pregnancy: 11.2 to 90 ng/mL
- Second trimester pregnancy: 25.6 to 89.4 ng/mL
- Third trimester pregnancy: 48.4 to 42.5 ng/mL
- Progesterone levels are usually higher when you are pregnant, but even in a non-pregnant patient they can reach 20 ng/ml. In a pregnancy cycle they should be greater than 10 to 12 ng/ml to have a better chance of a good pregnancy outcome.
- Only a pregnancy test that checks for the presence of the hCG human chorionic gonadotropin pregnancy hormone will tell you if you are pregnant or not. Even though progesterone levels are higher when you are pregnant, you cannot tell just by looking at a progesterone level whether you are pregnant or not. Progesterone levels can be high and you are not pregnant or they can be low and you are pregnant.
What to do with low progesterone levels
A low progesterone level especially a level below 10 ng/ml may mean that you did not ovulate. If you did ovulate,there are many different opinions as to what to do if the levels are low. Some doctors give progesterone (pills, shots, suppositories) and others don't treat unless there has been some proof of a preexisting low progesterone in non-pregnancy cycles.
Progesterone levels rise after ovulation, and the rise can usually be detected about a week after ovulation. There are no "normal" progesterone levels after ovulation, only low and elevated levels, and there is a wide variation in normal levels after ovulation.
- Progesterone levels after ovulation (midluteal, middle of the second half of the cycle) in a nonpregnant patient are generally at least 8-10 ng/ml. Much lower levels usually mean you did not ovulate.
- Progesterone levels can change from one day to the other, from one hour to the next, from one laboratory to the next.
- A single progesterone level, usually above or below 10ng/ml can asses the pregnancy viability
- After you eat, progesterone levels can drop by as much as 50%, that's why the blood test should be done in the morning and before you eat.
- Even on the same day women may have different levels.
- Progesterone levels are usually well below 5-10 ng/ml without ovulation.
- If you are pregnant, progesterone levels are usually at least 10-12 ng/ml to have a better chance of a good pregnancy outcome and most doctors like to see progesterone levels around 16-18 ng/ml or more though there are many successful pregnancies with lower levels.
- With an ectopic pregnancy, progesterone levels are lower when compared with an intrauterine pregnancy.
- There are differences in opinion as to what to do if progesterone levels are low after ovulation.
- Some doctors suggest giving progesterone (pills, shots, or suppositories) but many others do not treat unless you have IVF or injectable ovulation medications or if there has been proof of a preexisting low progesterone in nonpregnancy cycles and there are immune issues leading to miscarriages.
Can a low progesterone level predict an ectopic pregnancy?
According to a study done by Buckley and colleagues (Ann Emerg Med 2000 Aug;36(2):95-100) all patients with an ectopic pregnancy had a progesterone level below 22 ng/ml. Of the patients with a progesterone level below 22 ng/ml, 10% had an ectopic pregnancy, but none of the patients with progesterone over 22 had an ectopic pregnancy. Of the patients who did not have an ectopic pregnancy, 73% had a progesterone level below 22 ng/ml. This means that if your progesterone level is above 22 ng/ml, your chances of having an ectopic pregnancy according to this study was 2% or less. But even if your progesterone level is below 22 ng/ml, your chances of NOT having an ectopic is above 88%.
What is a false positive progesterone level
The two main reasons for an elevated progesterone level are: Ovulation and pregnancy. Other than after ovulation or pregnancy, progesterone levels can also be elevated with the following:
- Laboratory error due to cross reactivity with other hormones
- Taking progesterone pills or suppositories
- Ovarian cancer
- Adrenal cancer
- Aongenital adrenal hyperplasia, a group of disorders that affect your adrenal gland
Can progesterone show a false positive pregnancy HPT test
A pregnancy test checks for the presence of the hCG human chorionic gonadotropin pregnancy hormone. This hormone is very different than progesterone, and a progesterone elevation cannot give you a false positive pregnancy test.