Endometriosis is endometrial tissue including the glands and stroma localized outside the uterine cavity. This tissue like endometrial tissue in the uterus has steroid receptors which could respond to hormonal changes during the menstrual cycle. This normal inflammatory response is defined by the presence of internal bleeding coupled with inflammation, new blood vessel growth and the formation of fibrous tissue, which manifest the symptoms of the disease. 

Endometriosis is a widespread but most unrecognized benign disease of the female genital tract that often causes significant disability. Most patients suffer from severe pain and the overall influence of the condition on fertility produces severe psychological consequences. Mostly, the ectopic endometrial tissue occurs in the pelvic cavity in the ovaries, fallopian tubes, vagina, cervix, and uterosacral ligaments or rectovaginal fascia. They include symptoms like severe pain during menstruation, chronic pelvic pain as well as infertility among others. 

Estimating the prevalence of endometriosis is difficult because many women with the disease are asymptomatic and a definitive diagnosis requires a laparoscopic assessment. Endometriosis occurs in 10 to 15% of women of reproductive age but is present in up to 70% of women with chronic pelvic pain. In the U. S, 11.2% of women who were hospitalized due to genitourinary disorders positively tested for endometriosis, indicating a high healthcare expense. It frequently appears to be misdiagnosed due to its similar symptoms to other abdominal conditions; pain and infertility may be prolonged, and it is present in 50% of infertile women. The risk factors include early menarche, cycle regularity, heavy menstrual flow, and absence of parity, while the protective factors include childbirth, postpartum sterilization, oral contraceptive pill, and tubal ligation respectively. Alcohol moderate consumption is bad for the health but in this case, it increases the chances of endometriosis as compared to smoking. 

The exact causes of endometriosis are unknown and there are no hypothetical theories that would account for all the different subtypes of the disease while taking into consideration epigenetic and genetic factors, immunology, and the environment. Of all the theories proposed, Sampson’s theory has been known to be the most acceptable one. This means that during retrograde menstruation, blood and viable cells move from the uterus into the fallopian tubes and into the peritoneum, where it is alleged, they grow, causing inflammation. However, since retrograde menstruation has been reported in many women who do not experience endometriosis, this factor cannot fully explain the occurrence of the condition implying the presence of other contributing factors. There are other theories such as coelomic metaplasia theory and the vascular and lymphatic metastatic theory to account for the other forms of endometriosis. It is necessary to incorporate oxidative stress, ROS, as well as genetic, epigenetic, or environmental factors to have a broader perspective on the nature of the disease. 

The etiology of endometriosis involves multiple theories: 

Retrograde Menstruation: Menstrual blood moves in the opposite fallopian tubes and spills in the pelvic cavity endometrial cells embed and divide. 

Coelomic Metaplasia: There are peritoneal cells that line the wall of the pelvic cavity which under certain conditions metamorphose to epithelium of the endometria. 

Müllerian Remnants: Endometriosis may be due to embryonic rests arising from Müllerian ducts, which forms body’s reproductive organs. 

Lymphatic and Vascular Metastasis: This type of endometrial cells can also spread to other parts of the body through lymphatic or blood vessels. 

Endometriosis is a multifactorial disease with different hypotheses regarding its pathogenesis. According the most widely known Sampson’s theory, endometrial cells spread through the tubes and implant themselves to the peritoneal wall.  

It has been associated with oxidative stress, inflammation, hormonal dysregulation such as high estrogen levels as well as genetic factors. This results in chronic inflammation and high levels of certain pro-inflammatory cytokines that are detrimental to the disease’s progression. 

Untreated cases of the disease resolve spontaneously in up to one-third of all patients, although the disease evolves chaotically and therefore requires careful management. 

Age Group 

Reproductive Age: This condition has a higher prevalence in women in their childbearing age and particularly between 20 to 30 years of age, though younger and older women are not exempted either. These are usually expressed at puberty or at the time of the first menstruation. 

Adolescents: Endometriosis can manifest in teenagers through intense pain during menstruation or continuous pelvic pain, however; this condition is often difficult to diagnose in teens. 

Perimenopausal and Postmenopausal Women: Pain may be continuous or intermittent; if endometriosis has been detected earlier, it remains a factor in case of early menopause. 

Endometriosis presents itself with low abdominal pain and tenderness of the lower abdomen, which is most prominent during menstruation. Physical examination presents digitally palpable nodules along the uterosacral ligaments, the posterior uterus wall, or the cul-de-sac that are painful to compression. Fixed uterine retroversion and obliteration of the cul-de-sac may suggest extensive disease. Sometimes, it is possible to see a bluish vaginal nodule at the superior and posterior vaginal walls. Ovarian endometriomas can rupture and present acute pain, and extensive disease of the gastrointestinal tract can capacitate adhesions and obstruction. It should also diagnose cervicitis, abnormal discharge, and sexually transmitted diseases (STDs). 

• Infertility 
• Irritable bowel syndrome 
• Interstitial cystitis 

Chronic Pelvic Pain: Most commonly presents as CPP, and its symptoms are usually cyclical, but it may occur in other stages of the menstrual cycle as well. 

Severe Menstrual Pain (Dysmenorrhea): Pain is usually severe and may significantly limit the daily activities of the affected individual; the pain may progress gradually. 

Dyspareunia: Pain associated with sexual intercourse or afterwards tends to be rather frequent. 

Medical Management 

Pain Relief: 

• NSAIDs: Paracetamol and non-steroidal anti-inflammatory drugs such as ibuprofen are often used for pain relief. 

Hormonal Therapies: 

• Combined Oral Contraceptives: Minimize or stop menstrual bleeding which in turn reduces pain. 
• Progestins: Medications like medroxyprogesterone acetate may be prescribed to help decrease these symptoms. 
• GnRH Agonists: For instance, leuprolide or nafarelin will cause the endometrium to regress to menopausal status and thereby decrease the levels of estrogen hormone and the rate at which the endometrium will grow. It is normally applied in conjunction with add-back therapy with a view of reducing some of the side effects. 
• GnRH Antagonists: For example, elagolix works as the selective antagonist of gonadotropin-releasing hormone receptors but has a different set of side effects. 

Aromatase Inhibitors: 

• Letrozole: An adjunct to other treatments to lower estrogen levels to lose. 

Surgical Management 

• Laparoscopy: Diagnostic and Therapeutic: Employed for diagnosing and treating endometriosis either by excision or coagulation of the lesions. 
• Hysterectomy: Ovarian removal or not: It may be prescribed in severe conditions or when other therapies proved to be ineffective. Surgery to remove the ovaries (oophorectomy) may be done to minimize estrogen production. 

Lifestyle and Supportive Therapies 

• Diet and Exercise: Diabetes has also been associated with diet, and a balanced diet may be used to address some symptoms. 
• Exercise: Regular exercise also has been reported to help in the management of pain as well as general health of the individual. 

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Dietary Modifications: Includes diet counselling which encourages consumption of fruits, vegetables, whole grain products, lean proteins, and healthy fats. Others experience relief at eliminating certain foods which trigger the conditions such as gluten, dairy and high fat foods. 

Physical Activity: Aids overall health, relieve inflammation, and alleviate pain. Such form of exercises as Yoga or swimming exercises, going for a walk and or cycling can be of great assistance. Exercises can be done with the aim of enhancing the strength of pelvic muscles, correcting posture, as well as reducing pain. 

Heat Therapy: Heat on the lower abdomen is beneficial in relaxing muscles of the abdomen and thus alleviating discomfort due to sharp stomach cramps. 

Alternative Therapies 

Acupuncture: May even partly relieve pain and improve disease symptoms for patients. 

Acupressure: Refers to the use of pressure on part of the body with an aim of eradicating pain and balancing energy. 

Psychological Support: Psychotherapy which might take the form of cognitive behavioral therapy, or any other counselling model can aid in addressing the emotional psychological effects of chronic pain. There are many supports groups available that consist of people who also suffer from endometriosis they can offer comfort and advice on how to deal with the disease. 

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Desogestrel and ethinyl estradiol (Desogen, Ortho-Cept, Velivet, Azurette, Cyclessa): It inhibit the secretion of Lut Legends like Leydig cells and FSH from the pituitary gland. They accomplish this by lowering gonadotropin-releasing hormones (GnRHs) secreted by the hypothalamus part of the brain. This combination is also known as an oral contraceptive pill (OCP). Thus, all currently used formulations are equally effective; however, some newer or so called third generation pills have a higher progestogen component which may bring some advantages. 

Norgestimate and ethinyl estradiol (Ortho-Cyclen, Tri-Sprintec, Ortho Tri-Cyclen): It works in the same way by suppressing LH and FSH release from the pituitary gland due to decreased GnRH. 

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Norethindrone acetate: It is one of the most common types of progestin found in different types of oral contraceptives including Aygestin, Camila and Errin. In the treatment of endometriosis, the doses are much higher than those used for contraception purposes. 

Medroxyprogesterone: It is available in form of Provera or Depo-Provera, works by suppressing the growth of endometrial cells, which are shed in an orderly fashion once treatment stops. Although it does not always stop acute bleeding, it normally results in normal vaginal bleeding once the drug is discontinued. It is available in oral and intramuscular (depo) forms and is overall effective as well as may cause side effects like norethindrone. 

Megestrol (known by the trade name Megace): It produces results that are nearly as favorable as medroxyprogesteron 

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Goserelin: It is sold under the Zoladex is a drug that suppresses the secretion of ovarian and testicular steroids by reducing the levels of luteinizing hormone and follicular hormone. This compound is administered as an SC implant once a month in the upper abdominal region and exerts effects comparable to the other agents in this class. 

Leuprolide (as Lupron Depot): It also suppresses ovarian and testicular steroids through reduction of LH and FSH. It is produced in an SC form which should be taken once a day as well as an IM depot form which has to be administered once a month. 

Nafarelin: It is an analogue of GnRH, which was derived from the naturally occurring hormone and is 200-fold more potent. Chronic administration reduces the sensitivity of pituitary gland to endogenous GnRH and therefore less release of LH and FSH, decreased output of ovarian as well as testicular steroids. It is available as a nasal spray solution at a concentration of 2 mg/mL; however, it is taken two times per day as do the other drugs in this category. 

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Elagolix: It is also approved to handle the pain related to endometriosis, most particularly, moderate to severe pain. 

Relugolix/estradiol/norethindrone (Myfembree): It is a combination of relugolix, a GnRH receptor antagonist, estradiol, and norethindrone, a progestin. Used in the treatment of moderate to severe pain due to endometriosis in premenopausal women and for the management of heavy menstrual bleeding attributed to uterine fibroids (leiomyomas). 

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Danazol: It is a synthetic steroid used for the treatment of certain medical conditions associated with abnormal development of secondary sexual characteristics due to its antigonadotrophic action since it suppresses secretion of LH and FSH, as well as possessing weak androgenic activity. Although danazol has been known to be very effective in the management of endometriosis, it is rarely used today due to the side effects that have been associated with the drug and the availability of better drugs in the market. Some of these newer treatments might be cheaper or more appropriate for specific individuals. It usually takes about 3 to 6 months of usage of danazol to determine whether the drug has the intended effects. 

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Letrozole: It is marketed under the name Femara works as an aromatase antagonist, which inhibits estrogen synthesis among postmenopausal women. Although it has been established to offer good results in treating breast cancer, its use in managing endometriosis is not well proven. Letrozole has been reported to benefit the patients experiencing pain, especially if they have not been helped by other medication. While there are researches showing promise of aromatase inhibitors in the treatment of the disease it is significant to conduct further research to establish efficacy of aromatase inhibitors in treating endometriosis. 

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Laparoscopic Surgery: A procedure that involves using a laparoscope that is a thin tube with a camera, through small openings in the abdomen. Endometrial tissue is identified and removed or destroyed, ablated or excised). 

Hysterectomy: Surgical operation consisting of the excision of the uterus and in some cases the Fallopian tubes (oophorectomy). This may be done by using laparoscopic surgery or open abdominal surgery. 

Uterine Artery Embolization (UAE): Conducts involve the injection of chemicals into the arteries of the uterus to cancel the blood supply to the endometrial tissue. 

Endometrial Ablation: Different methods are applied to endometrial destruction including heat destruction or cold destruction. 

Symptom Management: The first step of treatment is to manage pain and to decrease the growth of endometrial tissue through the use of hormones such as combined oral contraceptive pills, progestins, GnRH agonists and anti-inflammatory drugs such as non-steroidal anti-inflammatory drugs. 

Surgical Intervention: In case of the failure of medical management or severe manifestation of endometrial disease, surgical management including laparoscopic surgery or hysterectomy may be used to remove or ablate endometrial lesions. 

Post-Surgical Management: Follow up interventions seek to minimize the risk of the tumor coming back, optimize the quality of patients’ lives, and this may involve prolonged hormonal therapy, fertility treatments if the patient wants children or wants to preserve his or her fertility, and dietary changes and stress management among others.