Progesterone is a steroid hormone which supports the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species (the process by which the embryo is formed and develops).
Progesterone belongs to a class of hormones called progestogens, and is the major naturally occurring human progestogen.
Progesterone is commonly manufactured from the soy or yam family, Dioscorea. Dioscorea contains large amounts of a plant sterol called diosgenin, which can be converted into progesterone in the laboratory.
Progesterone is produced in the ovaries (specifically after ovulation in the corpus luteum), the brain, and, during pregnancy, in the placenta.
In humans, increasing amounts of progesterone are produced during pregnancy:
Initially, the source is the corpus luteum that has been "rescued" by the presence of human chorionic gonadotropins (hCG) from the conceptus.
However, after the 8th week production of progesterone shifts to the placenta. The placenta utilizes maternal cholesterol as the initial raw material, and most of the progesterone produced in this manner enters the mother's bloodstream. Some progesterone, however, is picked up by the fetal circulation and used as the precursor for fetal corticosteroids. At term the placenta produces about 250 mg progesterone per day.
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