What is Progesterone?

Progesterone is one of the two primary female hormones. As the name implies, progesterone prepares ("pro") the womb for pregnancy (gestation). Progesterone works in tandem with estrogen ; indeed, if estrogen is taken as a medication without being balanced by progesterone (so called unopposed estrogen), there is an increased risk of uterine cancer.

However, progesterone is not well absorbed orally. For this reason, pharmaceutical manufacturers developed "progestins," substances similar to progesterone which are more easily absorbed. Most of the time, a woman prescribed "progesterone" is really being given a progestin. Two of the most commonly used progestins are medroxyprogesterone and norethindrone. However, it has been suggested that actual progesterone may offer benefits over...

Progesterone cream was widely promoted in the 1990s a treatment for osteoporosis , on the basis of meaningless “studies” whose designs were too poor to establish anything at all. ^{1 2} When properly designed studies were performed, the results were at best inconsistent. ³ Studies conflict on whether progesterone cream can help hot flashes. ⁴ One double-blind, placebo-controlled study failed to find any improvements in mood or general well-being in menopausal women using progesterone cream. ⁵ Like progestins, oral progesterone protects the uterus from the stimulating effects of unopposed estrogen. However, standard doses of progesterone cream probably provide too little progesterone to serve for this purpose (see next section).

Safety Issues

Even though progesterone is sold as a dietary supplement, it is a hormone, not a food. We recommend that it notbe used except under physician supervision.

Like progestins, true progesterone causes side effects. In one study, oral micronized progesterone at a dose of 400 mg per day was associated with dizziness, abdominal cramping, headache, breast pain, muscle pain, irritability, nausea, fatigue, diarrhea, and viral infections. ⁶