Progesterone is an important female sex hormone. Progesterone levels are normally elevated during the reproductive period of a woman’s life and become lower during menopause. Progesterone is produced by the corpus luteum and is necessary for proper uterine and breast development and function. Its levels are low during the follicular phase of the menstrual cycle and high during the luteal phase; they continue to rise during early pregnancy. High progesterone levels suggest pregnancy, ovarian cancer, or adrenal cancer, while low levels may occur in amenorrhea, fetal death, and toxemia of pregnancy.