Progesterone Levels are used in the evaluation of women who are having difficulty becoming pregnant or maintaining a pregnancy. It is also used to monitor “high-risk” pregnancies.
Progesterone acts primarily on the endometrium. It initiates the secretory phase of the endometrium in anticipation of implantation of a fertilized ovum. Normally progesterone is secreted by the ovarian corpus luteum following ovulation. In pregnancy, progesterone is produced by the corpus luteum for the first few weeks. After that the placenta begins to make progesterone. Both serum progesterone levels and the urine concentration of progesterone metabolites (pregnanediol) are significantly increased during the latter half of a normal ovulatory cycle. Progesterone levels provide information about the occurrence and timing of ovulation.
Because progesterone levels rise rapidly after ovulation, this study is useful in documenting whether ovulation has occurred and, if so, its exact time. This is very useful information in women who have difficulty becoming pregnant. A series of measurements can help define the day of ovulation. Plasma progesterone levels start to rise after ovulation along with luteinizing hormone (LH), and they continue to rise for approximately 6 to 10 days. The levels then fall and menses occurs. Blood samples drawn at days 8 and 21 of the menstrual cycle normally will show a large increase in progesterone levels in the latter specimen, indicating that ovulation has occurred. Serum progesterone levels can provide comparable information and are sometimes measured in lieu of endometrial biopsy to determine the phase of the menstrual cycle.
During pregnancy, progesterone levels normally rise because of the placental production of progesterone. Repeated assays can be used to monitor the status of the placenta in cases of “high-risk” pregnancy. Hormone assay for progesterone is used today to monitor progesterone supplementation in patients with an inadequate luteal phase to maintain an early pregnancy.
Normal Progesterone Levels
Normal Progesterone Levels are the lowest during childhood. Normal Progesterone Levels increase with aging and they are the highest among adult women. In adult women, Normal Progesterone Levels vary during the menstrual cycle and they increase during pregnancy. The following is a listing of Normal Progesterone Levels measured using Extraction Radioimmunoassay method:
Children younger than 16 years: Less than 20 ng/dL.
Adult Males: Between 10 and 50 ng/dL.
Normal Progesterone Levels in Adult Female
During Follicular Phase: Less than 50 ng/dL.
Luteal Phase: Between 300 and 2500 ng/dL.
Postmenopausal: Less than 40 ng/dL.
Pregnancy First Trimester: Between 725 and 4400 ng/dL.
Pregnancy Second Trimester: Between 1950 and 8250 ng/dL.
Pregnancy Third Trimester: Between 6500 and 22,900 ng/dL.
Causes of Progesterone Levels False Indications
- Recent use of radioisotopes may affect test results if testing is done by radioimmunoassay (RIA).
- Hemolysis caused by rough handling of the sample may affect test results.
- Drugs that may interfere with test results include Estrogen, Clomiphene, and Progesterone.
Causes of High Progesterone Levels
- Ovulation: This occurs with the normal development of a corpus luteum, which makes progesterone.
- Pregnancy: A healthy placenta produces progesterone to maintain the pregnancy.
- Luteal Cysts of Ovary: The corpus luteum produces progesterone in the nonpregnant female and in the early stages of pregnancy. Cysts can also produce progesterone for prolonged periods of time.
- Hyperadrenocorticalism, or Adrenocortical Hyperplasia: Adrenal cortical hormones are secreted at increased rates. 17-Hydroxyprogesterone is a precursor of these cortical hormones.
- Choriocarcinoma of Ovary: This tumor produces progesterone.
- Molar pregnancy: Hydatidiform mole can produce progesterone, although at lower levels than pregnancy.
Causes of Low Progesterone Levels
The following above obstetric emergencies are associated with decreased placental viability. Progesterone is made by the placenta during pregnancy. Decreasing values are seen when placental viability is threatened:
- Toxemia of Pregnancy.
- Threatened Abortion.
- Placental Failure.
- Fetal Death.
Ovarian Neoplasm: Ovarian epithelial cancers can destroy the functional ovarian tissue. Progesterone levels may decrease.
Amenorrhea, or Ovarian Hypofunction: Without ovulation, a corpus luteum will not develop. Progesterone will not be secreted and progesterone and pregnanediol levels will be lower than expected