Progesterone is produced by the ovary after ovulation. It instructs the uterine lining to stop growing so that it might develop and mature e in preparation for a possible pregnancy. Progesterone is produced for fourteen days after ovulation. If there is no pregnancy, progesterone decreases and signals the beginning of menses.

Progesterone decreases the target organ’s response to estrogen by decreasing the number of receptors the organ has for estrogen. Receptors are molecules on the cells that recognize specific hormones and allows them to carry their message to the cell.

Progesterone also decreases breast cell growth. It is involved in the maturation of breast cells and decreases the rate of multiplication. Progesterone also promotes normal cell death in the breast which is important in the prevention of cancer.

While estrogen decreases the rate of bone breakdown, progesterone stimulates bone osteoblasts. Osteoblasts are responsible for making new bone to replace old bone.

By decreasing thyroid-binding globulin, progesterone increases the activity of the thyroid hormone. The thyroid hormone increases metabolism and utilizes the fat stored under estrogen influence for energy. Normal progesterone levels are important for normal body composition. Low progesterone levels can lead to weight gain.

Progesterone stimulates normal sex drive because it can be converted to testosterone which is involved in male and female sex drive.

It blocks aldosterone receptors. Aldosterone promotes water retention and swelling. Progesterone blocks aldosterone causing normal fluid loss and decreasing swelling.

Progesterone decreases uterine muscle contractions which cause menstrual cramps by promoting uterine muscle relaxation. In the brain, progesterone binds GABA receptors. These receptors decrease anxiety, insomnia, and depression. Anti-depressants and barbiturates bind these same receptors. Progesterone is a natural antidepressant and prevents anxiety.