Progesterone is a hormone that occurs naturally in the body. It can also be made in a laboratory.

“Progestin” is a general term for a substance that causes some or all of the biologic effects of progesterone. The term “progestin” is sometimes used to refer to the progesterone made in the laboratory that is in oral contraceptives and hormone replacement therapy. However, all progesterone and progestin products are made in the laboratory. The term “natural progesterone” is really a misnomer. “Natural progesterones,” including the prescription products Crinone and Prometrium, are made from a chemical called diosgenin that is isolated from wild yam or soy. In the laboratory, this constituent is converted to pregnenolone and then to progesterone. The human body is not able to make progesterone from diosgenin, so eating wild yam or soy will not boost your progesterone levels.

Over-the-counter (OTC) progesterone products may not contain progesterone concentrations as labeled. According to a British report, two-ounce jars of Progest cream used in a clinical trial contained 100 mg progesterone per ounce rather than the 465 mg claimed by the manufacturer.

Topical progesterone products (preparations applied to the skin) marketed as cosmetics require no FDA approval prior to marketing. There is currently no limit on the amount of progesterone allowed in cosmetic products. In 1993 the FDA proposed a rule limiting progesterone-containing cosmetic products to a maximum level of 5 mg/oz with the product label instructing users not to exceed 2 oz per month. But this rule was never finalized.

Women take progesterone by mouth for inducing menstrual periods; and treating abnormal uterine bleeding associated with hormonal imbalance, and severe symptoms of premenstrual syndrome (PMS). Progesterone is also used in combination with the hormone estrogen to “oppose estrogen” as part of hormone replacement therapy. If estrogen is given without progesterone, estrogen increases the risk of uterine cancer.

Progesterone is also used to ease withdrawal symptoms when certain drugs (benzodiazepines) are discontinued.

Progesterone cream is sometimes used in hormone replacement therapy and for treating menopausal symptoms such as hot flashes. Topical progesterone is also used for treating or preventing certain allergies in which hormones play a role; and for treating bloating, breast tenderness, decreased sex drive, depression, fatigue, lumpy (fibrocystic) breasts, headaches, low blood sugar, increased blood clotting, infertility, irritability, memory loss, miscarriages, brittle bones (osteoporosis), bone loss in younger women, symptoms of PMS, thyroid problems, “foggy thinking,” uterine cancer, uterine fibroids, water retention, weight gain, and vaginal irritation (vulval lichen sclerosis).

Progesterone gel is sometimes used inside the vagina to expand the cervix (cervical ripening), treat breast pain in women with noncancerous breast disease, and to prevent and treat abnormal thickening of the lining of the uterus (endometrial hyperplasia).

Progesterone is also used intravaginally or by injection for treating infertility and symptoms of (PMS).

How does it work?
Progesterone is a hormone released by the ovaries. Changing progesterone levels can contribute to abnormal menstrual periods and menopausal symptoms. Progesterone is also necessary for implantation of the fertilized egg in the uterus and for maintaining pregnancy.

Lab-made progesterone is used to imitate the functions of the progesterone released by the ovaries.

Source: webmd.com