Progesterone is a steroid hormone made by the female reproductive system. The chemical plays a role in regulating reproduction. Progesterone pills are used in contraception, for relief of menopausal symptoms, in emergency contraception and to treat women with irregular menstruation.
Contraceptive progesterone pills are more accurately known as progestin pills. The term "progestin" refers to synthetic forms of the progesterone molecule. For example, one type of progestin used in oral contraceptives is known as norgestrel. Such synthetic progesterone mimics the action of natural progesterone.
Combination contraceptive pills contain both estrogen and progestin. Pills that only contain synthetic progesterone are known as progestin-only pills (POPs). These progesterone pills are safer for some women, including those who have high blood pressure, those who are breastfeeding, those who are over 35 and smoke, and those who have a history of blood clots.
Progesterone in the body is released by the corpus luteum in the reproductive system after ovulation. It prepares the lining of the uterus for potential pregnancy, and inhibits uterine contractions and the development of a new follicle. If pregnancy occurs, more progesterone is released by the placenta. If pregnancy does not occur, the secretion of progesterone diminishes and menstruation occurs.
The natural effects of progesterone mean progestins can be used to alter this sequence. When progesterone pills are taken orally before ovulation, the hormone prevents ovulation and acts as a contraceptive. Progesterone-only pills are slightly less effective than combination pills at preventing pregnancy.
Progesterone is also used in hormone replacement therapy. Hormone replacement therapy uses both estrogen and progesterone to treat women with menopausal symptoms. Estrogen can cause abnormal thickening of the uterus, which increases the risk of uterine cancer. Progesterone helps to regulate this thickening and reduce the risk of cancer.
For women with menstruation problems resulting from a lack of natural progesterone, supplementation with progesterone pills can restore a normal menstrual cycle. These pills are used only in women of childbearing age who have not yet reached menopause. In some cases, the woman's uterine lining does not respond to a normal level of progesterone and supplementation helps to prepare the lining of the uterus to thicken sufficiently for a fertilized egg to implant safely.
Progesterones such as levonorgestrel may also be used as an emergency contraceptive pill. The pill prevents ovulation and reduces the chance of pregnancy by 60 percent if taken within five days after having unprotected sex. Progesterone pills can, therefore, increase fertility, act as a regular contraceptive, help treat menopausal symptoms or act as an emergency contraceptive.
