Progesterone is one of two main hormones. the other being estrogen, made by ovaries of menstruating women. More specifically, it is the hormone made by the corpus luteum starting just prior to ovulation and increasing rapidly after ovulation to become the major female gonadal hormone during the latter two weeks of the menstrual cycle. It is necessary for the survival of the fertilized ovum, the resulting embryo, and the fetus throughout gestation when the synthesis of progesterone is taken over by the placenta. Progesterone is also made in smaller amounts by the adrenal glands in both sexes and by the testes in males, being an important step in the biosynthesis of adrenal cortical hormones. Its three major functions are:

1. The survival and development of the fetus

2. A broad range of intrinsic biologic properties such as protecting against the undesirable effects of unopposed estrogen

3. Its role as precursor of other steroid hormones such as estrogen and testosterone

The synthesis of progesterone originates in the ovary as a product of cholesterol which. From progesterone are derived not only the other sex hormones but also the corticosteroids. A simplified diagram of the steps in this process follows below.

IMPORTANT NOTE: These pathways represent the harmony and balance of a healthy metabolism. This balance is lost when synthetic hormones are introduced to the body.

Biosynthetic Pathway for Gonadal and Adrenocortical Hormones