Progesterone is made primarily by the corpus luteum (the follicle transformed after ovulation), and is a precursor to most sex hormones. Progesterone comes into action in the middle of the normal menstruating woman's cycle.
Stimulated by the release of LH (luteinizing hormone) in the form of pulses by the pituitary gland, progesterone is absolutely crucial to the survival of the ovum once fertilized. When pregnancy occurs, progesterone production increases rapidly and is taken over by the placenta. If the woman does not get pregnant, the corpus luteum shrinks, progesterone production falters and menstruation arrives.
Progesterone is the precursor, or parent, of estrogen in the ovaries. Adrenal glands and testes also manufacture it. Progesterone is the precursor of testosterone, all androgens, and other adrenal hormones, making it extremely important for reasons far beyond the sex hormone role.
Progesterone's function on the estrogen-progesterone team are to:
Progesterone's negatives are few and easily balanced by estrogen: