What Is It?
Endometriosis is a condition in which tissue similar to your uterine lining grows outside your uterus and gets stuck to other organs or structures, often resulting in pain or infertility. Endometriosis is a noncancerous condition in which tissue similar to the endometrium (uterine lining) grows outside your uterus and adheres to other pelvic structures, most commonly the ovaries, bowel, fallopian tubes or bladder. It is a common cause of pelvic pain and infertility.
It affects at least 5 percent of premenopausal women, and at least 5.5 million women in North America alone have endometriosis.
Historically thought of as a disease that affects adult women, endometriosis is increasingly being diagnosed in adolescents, as well.
Symptoms of Endometriosis
The most common symptoms are painful menstrual periods and/or pelvic pain.
* Diarrhea and painful bowel movements, especially during menstruation
* Intestinal pain
* Painful intercourse
* Abdominal tenderness
* Severe menstrual cramps
* Excessive menstrual bleeding
* Painful urination
* Pain in the pelvic region with exercise
* Painful pelvic examinations
It is important to understand that other conditions aside from endometriosis can cause any or all of these symptoms and other causes may need to be ruled out. These include, but are not limited to, interstitial cystitis, irritable bowel syndrome, inflammatory bowel disease, pelvic adhesions (scar tissue), ovarian masses, uterine abnormalities, fibromyalgia, malabsorption syndromes and, very rarely, malignancies.
Characteristics of Endometriosis
Endometrial tissue also may grow in the abdominal area or, more rarely, travel far from the pelvic region into the lungs, skin and other regions of the body. No matter where it goes, however, endometrial tissue continues to respond to hormonal signals--specifically estrogen--from the ovaries telling it to grow. Estrogen is the hormone that causes your uterine lining to thicken each month. When estrogen levels drop, the lining is expelled from the uterus, resulting in menstrual flow (you get your period). But unlike the tissue lining the uterus, which leaves your body during menstruation, endometriosis tissue is trapped in the pelvic cavity. With no place to go, the tissue bleeds internally. Your body reacts to the internal bleeding with inflammation, a process that can lead to the formation of scar tissue, also called adhesions. This inflammation and the resulting scar tissue may cause pain and other symptoms.
Recent research also finds that this misplaced endometrial tissue may develop its own blood supply to help it proliferate and nerve supply to communicate with the brain, one reason for the condition's severe pain and the other chronic pain conditions so many women with endometriosis suffer from.
The type and intensity of symptoms range from completely disabling to mild. Sometimes, there aren't any symptoms at all, particularly in women with so-called "unexplained infertility."
Risks of Endometriosis
If your endometriosis results in scarring of the reproductive organs, it may affect your ability to get pregnant. In fact, 30 to 40 percent of women with endometriosis are infertile. Even mild endometriosis can result in infertility.
Causes of Endometriosis
Researchers don't know what causes endometriosis, but many theories exist. One suggests that retrograde menstruation--or "reverse menstruation"--may be the main cause. In this condition, menstrual blood doesn't flow out of the cervix (the opening of the uterus to the vagina), but, instead, is pushed backward out of the uterus through the fallopian tubes into the pelvic cavity.
But because most women experience some amount of retrograde menstruation without developing endometriosis, researchers believe something else may contribute to its development.
For example, endometriosis could be an immune system problem or hormonal imbalance that enables the endometrial tissue to take root and grow after it is pushed out of the uterus.
Other researchers believe that in some women, certain abdominal cells mistakenly turn into endometrial cells. These same cells are the ones responsible for the growth of a woman's reproductive organs in the embryonic stage. It's believed that something in the woman's genetic makeup or something she's exposed to in the environment in later life changes those cells so they turn into endometrial tissue outside the uterus. There's also some thinking that damage to cells that line the pelvis from a previous infection can lead to endometriosis.
Some studies show that environmental factors may play a role in the development of endometriosis. Toxins in the environment such as dioxin seem to affect reproductive hormones and immune system responses, but this theory has not been proven and is controversial in the medical community.
Other researchers believe the endometrium itself is abnormal, which allows the tissue to break away and attach elsewhere in the body.
Endometriosis may have a genetic link, with studies finding an increase in risk if your mother or sister had the disorder. No specific genetic mutation has been clearly linked with the disease.
Gynecologists and reproductive endocrinologists, gynecologists who specialize in infertility and hormonal conditions, have the most experience in evaluating and treating endometriosis.
The condition can be very difficult to diagnose, however, because symptoms vary so widely and may be caused by other conditions.
Among the ways doctors diagnosis the disease are:
Laparoscopy. Currently, laparoscopy is the gold standard for the diagnosis of endometriosis and is commonly used for both diagnosis and treatment. Performed under general anesthesia, the surgeon inserts a miniature telescope called a laparoscope through a small incision in the navel to view the location, size and extent of abnormalities (such as adhesions) in the pelvic region.
However, merely looking through the laparoscope can't diagnose deep endometriosis disease, in which the endometrial tissue is hidden inside adhesions or underneath the lining of the abdominal cavity. More extensive dissection is needed to diagnose and treat this type of disease.
Many women have a combination of both deep and superficial (in which the endometrial tissue can be easily seen) endometrial disease.
Peritoneal tissue biopsy. During the laparoscopy, the doctor may remove a tiny piece of peritoneal tissue (the inner layer of the lining of the abdominal cavity) or other suspicious areas to help establish the diagnosis of endometriosis. This is recommended by the American College of Obstetricians and Gynecologists (ACOG), which notes that only an experienced surgeon familiar with the appearance of endometriosis should rely on visual inspection alone to make the diagnosis. A biopsy, however, is not mandatory to diagnose endometriosis, and a negative biopsy does not rule out the presence of this disease in other areas within the abdomen.
Ultrasonography, MRI and CT scan. An ultrasound uses sound waves to visualize the inside of your pelvic region, while an MRI uses magnets and a CT scan uses radiation. While these tests can suggest endometriosis or rule out other conditions, none can definitively confirm the condition.
At this point, there is no noninvasive method to diagnosis endometriosis, which is frustrating for both women and their health care providers.
Pelvic exam. Your doctor will perform a physical examination, including a pelvic exam, to aid in the evaluation. The examination will not diagnose endometriosis but may allow your doctor to feel nodules, areas of tenderness or masses on the ovaries that may suggest endometriosis.
Medical history. A detailed medical history may offer your health care professional the earliest clues in making the correct diagnosis. According to the Endometriosis Association, clues you may be at risk for endometriosis include pelvic pain; fatigue, exhaustion or low energy; diarrhea, painful bowel movements or other stomach upset around the time of your period; stomach bloating or swelling; or heavy or irregular periods. A simple five-question test about these conditions can quickly determine if you are at risk, but will not diagnose the disease.
There is no universal cure for endometriosis. However, there are a number of options available for treating and managing the disease after diagnosis. They fall into four categories: medical, surgical, alternative treatments and pregnancy.
1. Medical. The most common medical therapies for endometriosis are nonsteroidal anti-inflammatories (NSAIDs), hormonal contraceptives (in oral, patch or injectable applications) and other hormonal regimens, such as GnRH agonists (gonadotropin-releasing hormone drugs).
** Non-steroidal anti-inflammatories (NSAIDs). These drugs, such as ibuprofen, naproxen and aspirin, are often the first step in controlling endometriosis-related symptoms. They may be used long-term in a non-pregnant patient to manage symptoms, in part because they are effective at reducing implantation, are cheaper and easier to use than other options and have fewer side effects than hormonal treatments. However, some patients may experience severe gastrointestinal upset from these agents, particularly if they are administered for prolonged periods and at high doses. They are more effective when taken before pain starts.
** Contraceptive hormones (birth control pills). This option also costs less and has fewer side effects than other hormonal treatment options and may be recommended soon after diagnosis. Birth control pills stop ovulation, thus suppressing the effects of estrogen on endometrial tissue. In most cases, women taking hormonal contraceptives have a lighter and shorter period than they did before taking them. Often physicians will recommend using birth control pills continuously as opposed to cyclically to eliminate regular menstrual flow, which can be the cause of increased pain in some women with endometriosis.
** Medroxyprogesterone (Depo-Provera). This injectable drug, usually used as birth control, effectively halts menstruation and the growth of endometrial tissue, relieving the signs and symptoms of endometriosis. Side effects include weight gain, depressed mood and abnormal uterine bleeding (breakthrough bleeding and spotting), as well as a prolonged delay in returning to regular menstrual cycles, which can be of concern to women who want to conceive.
** Gonadotropin Releasing Hormone Drugs (GnRH agonists). These drugs block the production of ovarian-stimulating hormones, which prevents menstruation and lowers estrogen levels, thus causing endometrial implants to shrink. GnRH agonists usually lead to endometriosis remission during treatment and sometimes for months or years afterward. However, GnRH agonists have side effects, including menopausal symptoms like hot flashes, vaginal dryness and reversible loss of bone density. Add-back hormone therapy, which typically consists of a synthetic progesterone (progestin) administered alone or in combination with a low-dose estrogen, is typically prescribed along with GnRH agonists to alleviate these side effects.
** Danazol. This reproductive hormone is a synthetic form of a male hormone (androgen) and is available as Danocrine. It is used to treat endometriosis and works by directly suppressing endometrial tissue and suppressing ovarian hormone production. A woman taking danazol will typically not ovulate or get regular periods. Side effects may include weight gain, hair growth and acne, among others. Some of the side effects are reversible. Danazol is typically given for six to nine months at a time. Danazol is not a contraceptive agent, and it is critical that any woman taking this drug also use a barrier contraceptive (condoms, diaphragm, IUD) if she is sexually active.
** Aromatase inhibitors. This class of drugs inhibits the actions of the enzyme which forms estrogen in the body and can block the growth of endometriosis. It is important to understand that this class of drugs is not approved for use in the treatment of endometriosis by the U.S. Food and Drug Administration; it is under investigation. Side effects include hot flushes, bone loss and the potential for increased risk of birth defects if a woman conceives while taking these medications and remains on them. Their use should be limited to women participating in research trials or after obtaining written consent from a physician who is thoroughly familiar with this class of drugs.
2. Surgical. The goal of any surgical procedure should be to remove endometriotic tissue and scar tissue. Hormonal therapies may be prescribed together with the more conservative surgical procedures.
Surgical treatments range from removing the endometrial tissues via laparoscopy to removing the uterus, called a hysterectomy, often with the ovaries (called an oophorectomy). Surgery classified as "conservative" removes the endometrial growths, adhesions and scar tissue associated with endometriosis without removing any organs. Conservative surgery may be done with a laparoscope or, if necessary, through an abdominal incision.
** Laparoscopy. During a laparoscopy, an outpatient surgery also referred to as "belly-button surgery," the surgeon views the inside of the abdomen through a tiny lighted telescope inserted through one or more small incisions in the abdomen. From there, the surgeon may destroy endometrial tissue with heat, laser or by cutting it out. There is a risk of scar tissue, which could lead to infertility, making pain worse, or damaging other pelvic structures. Surgery to remove endometriosis involving the ureters and bowel can be especially complex and requires a high degree of surgical skill.
** Laparotomy. A laparotomy is similar to a laparoscopy but is more extensive, involving a full abdominal incision and a longer recovery period.
** Hysterectomy. During a hysterectomy, your uterus is removed. This leaves you infertile. Hysterectomy alone may not eliminate all endometrial tissue, however, because it can't remove tissue outside of the uterus or ovaries. Additionally, surgery to remove the uterus may not relieve the pain associated with endometriosis.
** Oophorectomy. Removing the ovaries with the uterus improves the likelihood of successful treatment with hysterectomy because the ovaries secrete estrogen, which can stimulate growth of endometriosis. It also renders you infertile, however.
If you wish to preserve your fertility, discuss other treatment options with your health care professional and consider seeking a second opinion.
There have been no comparative studies of medical and surgical therapies to see which approach is better. Each has advantages and disadvantages. Often, your plan of care will be a combination of treatments.
3. Alternative treatments. Alternative treatments for relieving the painful symptoms of endometriosis include traditional Chinese medicine, nutritional approaches, exercise, yoga, homeopathy, acupuncture, allergy management and immune therapy.
While some health care professionals may tell you these alternative paths to seeking pain relief from endometriosis are a waste of time, others may encourage you to try alternative methods of pain relief as long as they are not harmful to your condition. Either way, discuss any options you want to try with your health care professional. Also keep in mind that while these options may help relieve the pain of endometriosis, they won't cure the condition.
4. Pregnancy. While it can't be considered a "treatment" for endometriosis, pregnancy may relieve endometriosis-related pain, an improvement that may continue after the pregnancy ends.
Health care professionals attribute this pregnancy-related relief to the hormonal changes of pregnancy. For example, ovulation and menstruation stop during pregnancy, and it's menstruation that triggers the pain of endometriosis.
Plus, endometrial tissue typically becomes less active during pregnancy and may not be as painful or large without hormonal stimulation. However, in many cases, once the pregnancy and breastfeeding end and menstruation returns, symptoms also return.
If endometriosis has caused infertility, you have several treatment options, including surgery, drugs to stimulate ovulation, typically administered with intrauterine insemination or in vitro fertilization. The appropriate approach would be based on the results of a complete evaluation including an assessment of the male partner. In general, medicines that suppress the painful symptoms of endometriosis, such as GnRH agonists, oral contraceptives and danazol, do not improve the likelihood of pregnancy. The only possible exception would be that the use of a course of GnRH agonists before in vitro fertilization may improve outcomes in certain endometriosis patients, according to several recent studies.
There is no known way to prevent endometriosis. However, some health care professionals believe there might be a certain level of protection against the disease if you begin having children early in life and have more than one child.
Additionally, you may prevent or delay the development of endometriosis with an early diagnosis and treatment of any menstrual obstruction, a condition in which a vaginal cyst, vaginal tumor or other growth or lesion prevents endometrial tissue from leaving your body during menstruation.
There also is some evidence that long-term birth control pill users are less likely to develop endometriosis.
Facts to Know
1. Endometriosis is a noncancerous condition that affects at least 5 percent of reproductive-age women.
2. About 5.5 million women in the United States and Canada have been diagnosed with endometriosis.
3. Endometriosis develops when cells from the endometrium--or uterine lining--grow outside the uterus and stick to other structures, most commonly the ovaries, bowel, fallopian tubes or bladder. Endometrial tissue may migrate outside of the pelvic cavity to distant parts of the body. Researchers aren't sure what causes this condition.
4. Symptoms of endometriosis can range from mild pain to pain severe enough to interfere with a woman's ability to lead a normal life. Other symptoms include heavy menstrual bleeding, cramping, diarrhea and painful bowel movements during menstruation, and painful intercourse. However, you may have the disease and experience none of these symptoms.
5. A laparoscope is commonly used to diagnose and treat endometriosis. Laparoscopy allows a surgeon to view abnormalities in the pelvic region via a miniature telescope inserted through the abdominal wall, usually through the navel. While this is the best method of diagnosis available, it doesn't rule out endometriosis just because the doctor doesn't see any endometrial tissue.
6. Hormonal changes that occur during pregnancy can temporarily halt the painful symptoms of endometriosis since menstruation stops and estrogen levels drop.
7. There is no cure for endometriosis. Treatment options include minor and major surgery and medical therapies, including hormonal contraceptives and other hormonal drugs, such as GnRH (gonadotropin-releasing hormone) agonists, that limit the estrogen release that stimulates endometrial tissue growth.
8. There is some evidence that a family history of endometriosis may contribute to your likelihood of developing this disease. If you have a mother or sister who is battling endometriosis or has been diagnosed with it, your risk of developing the disease is higher than someone with no family history.
Questions to Ask
Review the following Questions to Ask about endometriosis so you're prepared to discuss this important health issue with your health care professional:
1. How many cases of endometriosis do you treat per month?
2. How do you make the diagnosis?
3. How many laparoscopic and/or laparotomy procedures do you perform each month for endometriosis and how do you typically treat the disease during surgery?
4. Do you always use medical therapy before surgical therapy? If so, what therapies do you use?
5. Do you use GnRH agonists? If so, when? Before or after surgery?
6. What kinds of hormonal drug therapies have you used for patients with endometriosis?
7. Do you prescribe add-back therapy with GnRH agonist therapy? What add-back hormones do you use and why? Are there other options I can consider?
8. What side effects might I experience with the different hormonal therapies? How long do I have to be on these drugs for them to work effectively? Will my endometriosis come back when drug treatment ends?
9. Does endometriosis affect my ability to have children?
10. Do you think that alternative treatments--such as traditional Chinese medicines, changes in diet, homeopathy or allergy management--may help reduce the pain associated with endometriosis? Can you refer me to any practitioners who specialize in these areas and might be helpful to me?
11. When you perform laparoscopy for endometriosis, are you prepared to treat any disease that you see at that time or do you perform a diagnostic procedure only? What surgical approaches do you typically employ to treat endometriosis (for example, ablation, excision, laser, coagulation)?
12. If I want to conceive or am having trouble getting pregnant and have a diagnosis of endometriosis, how would this change your treatment plan? What treatments for infertility do you offer and what are the success rates in my circumstance?
1. What causes endometriosis?
The most widely accepted cause of endometriosis is retrograde menstruation. This occurs when tissue from the uterine lining, called endometrial tissue, flows backward through your fallopian tubes while you're menstruating. The tissue gets trapped and can't leave the body.
However, no matter where it is in the body, endometrial tissue still responds to your hormones each month. This tissue can become inflamed, bleed and develop into scar tissue. When the tissue is attached to organs in the pelvic and abdominal cavities, it may cause severe pain, infertility and other problems.
Other theories suggest that alterations in the immune system response, hormonal imbalances or environmental causes may be related to the development of endometriosis. Experts find strong evidence suggesting a genetic link.
2. What does endometriosis feel like?
Pain in the pelvic region ranging from very mild to severe is the most common symptom, but you may not experience any symptoms. Some women describe the pain as sharp and burning. It may last all month long, but is usually worse during menstruation, deep penetration during intercourse or bowel movements. Other symptoms may include:
** Diarrhea and painful bowel movements especially during menstruation
** Abdominal tenderness
** Intestinal pain
** Abnormal menstrual bleeding
** Severe menstrual cramps
** Pelvic pain distinct from menstrual cramps
** Pain during or after sexual penetration
** Painful bowel movements
** Pain with exercise
** Pain with urination
** Painful pelvic examination
3. How can I be sure I'm being diagnosed correctly if pain associated with the disease can often be confused with other medical problems?
Even without a definitive diagnosis, your health care professional may still prescribe hormonal treatments. If the pain decreases, there is an assumption that endometriosis was the cause of the pain. However, endometriosis cannot be definitively diagnosed without laparoscopy and biopsy.
4. Can I get pregnant if I have endometriosis?
Yes, you can. The majority of women who have endometriosis are fertile, and there are many who have the disease and go on to have children. However, the likelihood of infertility does increase in women with endometriosis of all stages.
5. Is there any way I can prevent endometriosis?
No. Experts don't know definitively what causes the condition so they don't know how to prevent it. Research suggests that having children early, having more than one child and long-term use of oral contraceptives may reduce the risk. However, many other factors determine if and when a woman should have children.
6. What options are available to treat endometriosis?
The most common medical therapies for endometriosis are hormonal contraceptives and other hormonal regimens, such as GnRH agonists (gonadotropin-releasing hormone drugs), which reduce estrogen release, limiting the effects of hormones on the endometrial tissue. Danazol, a synthetic androgen, is also used, but it can cause some undesirable side effects, including weight gain, hirsutism (hair growth) and lowering of the voice. Surgical treatments range from removing only the endometrial implants via laparoscopy to removing the uterus and ovaries.
7. How do I know which is the best treatment option for my case of endometriosis?
It's tough to know which treatment is best for you, especially since very few comparative studies have been conducted to determine which approach is better. There are pros and cons for all treatments. Most women with the disease can find relief via medical therapies, and birth control pills may be used indefinitely to manage symptoms. Other women turn to surgery. However, many women try to avoid surgery to remove the uterus because it's a serious procedure that will leave them infertile and carries no guarantee of banishing endometriosis forever.
Because of the risks associated with surgery, the usual course of treatment is to proceed from the least invasive or risky to the more invasive treatment. That means medical treatment first.
If that doesn't work, your doctor may recommend laparoscopy, with surgery to remove the uterus as a last resort.
1. Boost intake of omega-3s
Animal research suggests that the omega-3 fatty acids found in fatty fish like mackerel, salmon, sardines and anchovies may help ease the pain of endometriosis. No research has been done on women with endometriosis to date, but some health care professionals recommend fish oil supplements to their patients with the condition. Fish oil has many other health benefits as well. Talk with your doctor about this option.
2. Eliminate trans fats
Recent research shows a link between high dietary intakes of trans fats from hydrogenated oils and increased risk of endometriosis--another good reason to substitute healthful omega-3s for trans fats.
3. Block prostaglandin to relieve pain
Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) are enough to benefit many women with pain from endometriosis and may be the most helpful choice for you as well--check with your health care professional. Ibuprofen (Advil, Motrin, Rufen) and naproxen (Aleve, Anaprox, Naprosyn) are all examples. These drugs block prostaglandins. Prostaglandins are natural body substances that promote inflammation, uterine contractions and pain and are thought to be linked to endometriosis.
4. What to do when pain remedies don't work
Make sure your body is best able to withstand pain by getting enough sleep at night, eating right and taking recommended doses of vitamins and minerals--some studies suggest good results with magnesium or thiamine. A heating pad or hot bath may help ease painful cramps. Relaxation techniques, meditation and even acupuncture have helped some women--see a pain management specialist or visit a pain center. Other possibilities include prescription pain control drugs, hormone therapy, trancutaneous electrical stimulation (TENS) and surgery to remove endometriosis lesions or to cut nerves transmitting pain.
5. Get help for painful intercourse
Tell your health care professional and ask for help, as painful intercourse is a symptom of endometriosis. Women typically feel pain during deep penetration and some feel pain as if something has been "bumped into." Your health care professional will need to ask questions and perform a pelvic examination to find abnormalities and the source of tenderness. Ultimately, you may need a laparoscopy to document the presence of endometriosis lesions, and medication or surgery to relieve pain.
6. Prepare for Laparoscopy
Schedule your procedure at the end of the week, to take advantage of the weekend as part of your recovery time. The procedure is typically performed during the first half of the menstrual cycle before ovulation but after the menstrual flow has stopped. Clear your schedule for a few weeks afterward to allow as much time as possible for rest. Clean and take care of errands in advance, and lay in a supply of convenience meals. Arrange with your partner or an adult friend to help you with transportation on the day of surgery. Don't eat anything heavy or fatty the evening before, follow your doctor's preoperative instructions, leave jewelry and valuables at home and arrive early to fill out forms.
Organizations and Support
For information and support on coping with Endometriosis, please see the recommended organizations, books and Spanish- language resources listed below.
American Association of Gynecologic Laparoscopists (AAGL)
Address: 6757 Katella Avenue
Cypress, CA 90630
Hotline: 1-800-554-AAGL (1-800-554-2245)
American College of Obstetricians and Gynecologists (ACOG)
Address: 409 12th Street, SW
P.O. Box 96920
Washington, DC 20090
American Society for Reproductive Medicine (ASRM)
Address: 1209 Montgomery Highway
Birmingham, AL 35216
Association of Reproductive Health Professionals (ARHP)
Address: 1901 L Street, NW, Suite 300
Washington, DC 20036
Center for Endometriosis Care
Address: 1140 Hammond Drive
Building F, Suite 6220
Atlanta, GA 30328
Endometriosis Association (EA)
Address: 8585 N. 76th Place
Milwaulkee, WI 53223
Endometriosis Research Center
Address: 630 Ibis Drive
Delray Beach, FL 33444
A Gynecologist's Second Opinion: The Questions & Answers You Need to Take Charge of Your Health
by William H. Parker, Rachel L. Parker
Coping With Endometriosis
by Robert Phillips, Glenda Motta
Endometriosis: One Woman's Journey
by Jennifer Marie Lewis
Endometriosis Survival Guide: Your Guide to the Latest Treatment Options and the Best Coping Strategies
by Margot Fromer
Endometriosis: The Complete Reference for Taking Charge of Your Health
by Mary Lou Ballweg
Living Well with Endometriosis: What Your Doctor Doesn't Tell You ... That You Need to Know
by Kerry-ann Morris
100 Questions & Answers About Endometriosis
by David B. Redwine
Yale Guide to Women's Reproductive Health: From Menarche to Menopause
by Mary Jane Minkin, Carol V. Wright
American Academy of Family Physicians, Family Doctor: Endometriosis
Endometriosis Association On-Line
Address: La Endometriosis Association Oficinas Internacionales
8585 N. 76th Place
Milwaukee, WI 53223
"Endometriosis." The Mayo Clinic. September 11, 2010. http://www.mayoclinic.com/health/endometriosis/DS00289. Accessed May 2011.
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"Take the test." The Endometriosis Association. 2005. http://www.endometriosisassn.org/take-the-test.html. Accessed May 2011.
"A prospective study of dietary fat consumption and endometriosis risk." Hum Reprod. 2010 Jun;25(6):1528-35. Epub 2010 Mar 23. http://www.ncbi.nlm.nih.gov/pubmed/20332166. Accessed May 2011.
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Berkowitz, Ross, Robert L. Barbieri, Andrea E. Dunaif. Kistner's Gynecology and Women's Health. 7th ed. St. Louis: Mosby, 1999. pp. 501-502.
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Hulley S, Furberg C, Barrett-Connor E, et al, for the HERS Research Group. Heart and estrogen/progestin replacement study follow-up (HERS II): Part 2. Non-cardiovascular outcomes during 6.8 years of hormone therapy. JAMA 2002;288:58- 66.
Writing Group for the Women's Health Initiative Investigators. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women's Health Initiative randomized controlled trial. JAMA 2002; 288:321-333.
"Estrogen Plus Progestin Study Stopped Due to Increased Breast Cancer Risk, Lack of Overall Benefit." National Heart, Lung and Blood Institute. http://www.nhlbi.nih.gov. Updated July 9, 2002; accessed July 9, 2002.
"Women's Health Initiative," National Heart, Lung and Blood Institute. http://www.nhlbi.nih.gov. Updated July 9, 2002; accessed July 9, 2002.
"The Women's Health Initiative New Facts About: Estrogen/Progestin Therapy." National Heart, Lung and Blood Institute. http://www.nhlbi.nih.gov. Updated July 9, 2002; accessed July 9, 2002.
"Use of Hormone Replacement Therapy Questioned For Some Women: A Preliminary Response from The North American Menopause Society." http://www.nams.org. Updated July 9, 2002; accessed July 9, 2002.
Lacey JV, Mink PJ, Lubin JH, et al. "Menopausal Hormone Replacement Therapy and Risk of Ovarian Cancer." JAMA. 2002;288:334-341.368-369.
Droegemuller, William. "Endometriosis and Adenomyosis: Etiology, Pathology, Diagnosis and Management," in Comprehensive Gynecology, 4th Ed., Stenchever, Droegemuller, Herbst, Michell (2001), p. 531-564.
"About DES (diethylstilboestrol)" Endometriosis.org. http://www.endometriosis.org. Dated 1999. Accessed August 2001.
"Endometriosis Family Study Identifies High Risk of Cancer and Autoimmune Diseases." Endometriosis Association. http://www.endometriosis.org. Dated 1999. Accessed August 2001.
Guidelines on the Treatment of Endometriosis: Update. American College of Obstetricians and Gynecologists (ACOG). Practice Bulletin no. 11, Obstetrics and Gynecology, December 1999.
Reproductive Conditions-Endometriosis. Veritas Medicine. http://www.veritasmedicine.com. Dated 2001. Accessed August 2001.
The Endometriosis Association. http://www.endometriosisassn.org. July 2005.
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Berkley KJ, Rapkin AJ, Papka RE. The pains of endometriosis. Science. 2005 Jun 10;308(5728):1587-9.