The corpus luteum of the ovary creates a steroid hormone known as progesterone during ovulation. Although this is also produced by the adrenal glands, the ovaries produce the majority of the body's supply. This is basically an originator for other hormones such as cortisol, estrogen, testosterone, and androstenedione. Approximately 20 to 30 mg of this hormone are produced during menstruation.

This hormone plays an important part in balancing the production of estrogen. It also helps prevent osteoporosis by stimulating bone building. It is important that the level of progesterone does not drop below normal level and must be produced in sufficient quantity by the body. Progesterone is mostly used during the hormone replacement therapy.

Progesterone, when applied externally, is easily absorbed into the skin since it is fat-soluble. It is best absorbed at places where the skin is soft such as the breasts, inner thighs, and hands.

The body begins producing more estrogen a few years before menopause, but the amount of progesterone being produced decreases at this time. In such cases progesterone cream can be applied externally to combat the extra estrogen, as more estrogen can result in PMS. Even when the body is capable of producing sufficient amount of progesterone, constant anxiety can sometimes hinder its production.

Progesterone is produced in a large quantity during the last trimester of pregnancy so external application can be reduced at this time. Excess progesterone can cause insomnia as well as hormone imbalance.