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The naturally occurring hormone progesterone means literally, ''for gestation'' - it is the hormone of pregnancy. Produced by the ovaries and adrenal glands, progesterone prepares the lining of the uterus for the fertilized ovum and maintains pregnancy. Specifically, progesterone converts the womb lining into a soft spongy bed in order to enhance implantation of a fertilized egg. If implantation does not occur, progesterone levels fall and menstruation begins. Progesterone also affects contractions of the fallopian tubes, thickens the consistency of vaginal mucus, and raises body temperature slightly. During a woman's reproductive years, progesterone levels in the body fluctuate in a cyclic pattern. During the first half of the menstrual cycle, the concentration of progesterone in the bloodstream is less than 1 ng/ml. During the second half, or luteal phase, progesterone in the bloodstream ranges from 3 ng/ml to 25 ng/ml. Very high levels of progesterone are necessary to maintain a pregnancy. When pregnancy occurs, the placenta takes over output of progesterone, producing levels up to 30 times greater than normal peak levels. Following birth, the progesterone level drops abruptly. A woman's progesterone level naturally declines during perimenopause, and menopause, and after a hysterectomy, where the ovaries have been removed, as do her levels of estrogen and testosterone. |
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