Progesterone is a hormone released by the corpus luteum in the ovary. It plays important roles in the menstrual cycle and in maintaining the early stages of pregnancy. It may also be involved in the growth of certain cancers.
I've been following various people's posts about the GRE for 10 months now. Some people don't study at all for the GRE, some study for a weekend, the average is about 2 to 3 months, and some study for a year or more.
The GRE is offered at testing centers almost every day. Call your local center for details and to book your test. While in theory you could sign up for the GRE with only two days' notice, don't depend upon this luxury. Call at least one month prior to your desired test date.