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Ethinyl Estradiol (Synthetic Estrogen)


Updated May 16, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Ethinyl Estradiol (Synthetic Estrogen)

Ethinyl Estradiol

Photo © 2012 Dawn Stacey

Estrogen is a hormone usually produced by the female ovaries and is crucial for normal female reproductive functioning. Estradiol is natural occurring form of estrogen. It helps the female reproductive organs to mature as well as helps the uterine wall prepare for the implantation of a fertilized egg.

Ethinyl estradiol (EE) is a synthetic form of estrogen and is mainly used in various hormonal contraceptives -- usually in combination with a progestin. It is one of the most commonly used medications. Hormonal birth control containing ethinyl estradiol include:

Over the years, the amount of the synthetic estrogen, ethinyl estradiol, in birth control formulations has greatly decreased to safer levels. Interestingly, when the first birth control pill, Envoid, gained FDA approval in 1960, it did not even contain ethinyl estradiol. Envoid’s formulation consisted of a progestin and 150 micrograms (mcg) mestranol (a type of estrogen that is converted in the body to an ethinyl estradiol). To help put this estrogen level into perspective, 50 mcg of mestranol is equal to about 35 mcg of ethinyl estradiol, so the original birth control pill contained the equivalent to 105 mcg of this synthetic estrogen. Most combination birth control pills today contain between 20 mcg (low dose pills) to 30/35 mcg of ethinyl estradiol. However, there are some higher-dose pills that do contain up to 50 mcg and there is one low dose pill, Lo Loestrin 1/10 that only has 10 mcg ethinyl estradiol.

The NuvaRing contains steadily releases 15 mcg of ethinyl estradiol daily into the body over a period of 21 days. The Ortho Evra Patch delivers 20 mcg of ethinyl estradiol each day for a duration of 7 days, yet because of the way the body absorbs this hormone, your overall exposure to the ethinyl estradiol in the patch is comparable to a daily 50 mcg birth control pill. That being said, overall, recent contraceptive formulations contain less than one third of ethinyl estradiol than earlier versions of the pill.

The lower ethinyl estradiol amounts now available in hormonal contraception enable women to obtain both the contraceptive and non-contraceptive benefits of birth control without as many of the unpleasant side effects. Ethinyl estradiol can assist in regulating your period or help manage painful periods. Because it helps to suppress ovulation, this synthetic estrogen has also been found to lower your risk of ovarian cancer, and due to estrogen’s ability to block bone resorption, ethinyl estradiol may help to increase bone mineral density.

Because ethinyl estradiol is broken down very quickly in the body (liver), birth control pills need to be taken at the same time each day. If not, the estrogen may be metabolized too quickly, and the pill’s effectiveness can be lowered. Certain medications may also cause the liver enzymes to speed up the body's break-down of estrogen or lower the re-circulation of available estrogen within the body -- both of which can lead to decreased ethinyl estradiol levels and greater chances of pill failure.

Finally, there are some women who should not use hormonal contraceptives that contain ethinyl estradiol. Higher estrogen exposure may be linked to blood clots/VTE. This risk increases for women who smoke or have specific medical conditions. Some research even suggests that, in order to be effective, severely overweight women may need to use contraceptives with higher levels of ethinyl estradiol. Due to potential side effects and/or certain conditions which may lower the safety or effectives of hormonal contraception, it is critical that you fully (and honestly) discuss your lifestyle habits and medical history with your doctor to determine if you are a good candidate for contraceptives that contain ethinyl estradiol.

Pronunciation: Ethinyl /eth•i•nyl/ [eth´ĭ-nil] Estradiol /es•tra•di•ol/ [es′trədī′ôl] (Estrogen: /ES•troh•jen/ [es′trojən])
Also Known As: Estrogen, Ethinyl, Ethinylestradiol, Synthetic estrogen, Estrogen in the pill, Mestranol, EE, Envoid
Alternate Spellings: Ethinylestradiol rather than Ethinyl Estradiol; Oestrogen
The synthentic estrogen, ethinyl estradiol (along with a progestin) is widely found in hormonal birth control formulations. Adding this hormone appears to help stabilize the endometrium as well as diminish unwanted spotting.

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