Estrogen and progesterone are two hormones naturally produced in women's bodies. In the course of ovulation, or egg production, they send signals to the breasts and uterus in advance of potential fertilization. Synthetic forms of estrogen and progesterone are also combined in products designed for birth control and hormone replacement therapy.
Birth Control
Most birth control pills contain a combination of synthetic estrogen and progesterone, according to the Nemours Foundation. These products achieve their effects by preventing ovulation and decreasing sperm's access to the uterus. In addition to these functions, use of combination birth control pills can decrease your risks of developing ovarian or endometrial cancer, the American Congress of Obstetricians and Gynecologists reports. Use of combination birth control also promotes lighter, shorter intervals of menstrual bleeding.
Continuous Dosing
Normally, when using combination birth control pills, you take hormones for 21 straight days, then take a weeklong break from treatment, according to the American Congress of Obstetricians and Gynecologists. Recently, doctors have developed a new method of pill administration---called continuous dosing---which provides combined hormones for 84 days, followed by a weeklong break. If you have painful periods, fibroids or endometriosis, use of continuous dosing can help diminish your symptoms by reducing your number of menstrual periods.
Hormone Replacement
Hormone replacement therapy, or HRT, is a technique sometimes used to diminish adverse effects of menopause and prevent osteoporosis and colorectal cancer, according to the American Academy of Family Physicians. Prior to 2002, women often received combined estrogen and progesterone HRT for five years or longer. That year, a group of studies known as the Women's Health Initiative determined that use of HRT on this level significantly increases a woman's risk of developing several serious medical conditions, including blood clots, strokes, heart attacks and breast cancer. However, you may still receive short-term combined HRT if you do not have a history of blood clots or heart disease.
Progesterone-Only Pills
Some birth control pills contain synthetic progesterone---also called progestin---without any estrogen, the American Congress of Obstetricians and Gynecologists notes. Your doctor may recommend this type of pill if you are breastfeeding or have health problems that prevent the use of estrogen. In some cases, use of low-dose progesterone-only pills may slightly elevate your chances of getting pregnant when compared to combination products.
Considerations
The American Congress of Obstetricians and Gynecologists lists potential side effects of combination birth control pills that include headaches, nausea and breast tenderness. In many cases, these symptoms will ease after several months of regular pill use. You can also diminish potential side effects by taking your pill at a regular time each day. Smoking while on birth control can trigger increased side effects, the Nemours Foundation notes.
