I went to a website and I found this for you:
What is Progesterone?
Progesterone is an important hormone manufactured by the adrenal glands in men and women. In women progesterone is also produced in the ovaries after ovulation (release of an egg) and in the placenta during pregnancy. Progesterone is responsible for many functions throughout the body and is also used by the body to produce other hormones.
What does it do?
The cycle of hormones that allows a woman to conceive is one of the most complicated systems in our body. Medical science does not fully understand the menstrual cycle and there are many different hormones involved.
For simplicity the menstrual cycle is often described in terms of estrogen and progesterone although in reality many other hormones are also involved. During the first half of a woman's menstrual cycle estrogen levels increase during the first half of the cycle, peaking at ovulation. Progesterone production begins just prior to ovulation, and increases rapidly until it reaches a peak production of about 20 mg/day. If the egg is not fertilized, the production of progesterone (as well as that of estrogen) slows, then stops, triggering the menses. If the egg is fertilized the placenta will produce 300 to 400 mg/day of progesterone during pregnancy.
many women use NPC to conceive. Many women also use it to bring on AF.
HTH!!! | 
What is NPC? 
