A progesterone test measures the amount progesterone in a blood sample. Progesterone, a female hormone produced by the ovaries during ovulation, helps prepare the lining of the uterus (endometrium) to receive the egg if it becomes fertilized by a sperm. If the egg is not fertilized, progesterone levels will drop and menstrual bleeding begins. During pregnancy, the placenta produces high levels of progesterone as well, starting near the end of the first trimester and continuing until the baby is born. Levels of progesterone in a pregnant woman are almost 10 times higher than they are in a woman who is not pregnant.
Certain types of cancer cause abnormal progesterone levels in men and women.
