More specifically, it is produced by the corpus luteum just after ovulation. Progesterone is responsible for preparing and maintaining the lining of the uterus in preparation for the fertilized egg. Progesterone secreted from the ovary is necessary for the survival of the ovum and the resulting embryo until the placenta takes over this production. The decline in progesterone each month triggers the menstrual cycle. Progesterone and estrogen are closely interrelated and their actions in the body are in a delicate balance.
Progesterone is a natural hormone produced by the ovaries.
Synthetic progestins are made from natural progesterone. Natural micronized progesterone is obtained from wild yams or soybeans as a precursor substance called diosgenin. This is then converted in the lab to progesterone. It is exactly the same as the progesterone produced by the ovaries. Any woman taking estrogen replacement therapy who still has a uterus should take progesterone.