Progesterone

Progesterone is a steroid hormone (classified as a progestin) that
is the precursor of all the other major classes of steroid hormone
(Figure 19.24). Progesterone
is a progestin that is synthesized from pregnenolone.
(see here).
See also: Steroid
Metabolism, Steroid Hormones,
Steroid Hormone Synthesis Cholesterol
Biosynthesis, Cholesterol,
RU486, Steroid
and Thyroid Hormones - Intracellular Receptors
INTERNET LINK: Steroid
Hormone Metabolism