Although little is known about the causes of endometriosis, it is reported that women with endometriosis have a high rate of comorbidity with other chronic pain syndromes associated with peripheral and central changes in pain processing, including fibromyalgia, migraine headaches, inflammatory bowel disease, and painful bladder syndrome. Later, various studies conducted in different years showed that cross-organ sensitivity phenomenon, defined as the spread of harmful inputs (inflammation products, mediators, pathogens, etc.) from a diseased visceral organ to a normal organ, comorbidities including IBS, IBD, interstitial cystitis and chronic pelvic pain disorders are common. Therefore, it has been suggested that patients with endometriosis may have a higher risk of developing these chronic diseases. The results of another study are inconsistent with the studies that supports the coexistence of endometriosis and fibromyalgia.~These literature data indicate the need for more data on the frequency of fibromyalgia in women with endometriosis. On the other hand, it has been reported that pain scores are correlated with daily fluctuations of progesterone and testosterone in women with fibromyalgia, and progesterone and testosterone play a protective role for fibromyalgia pain. Dienogest is a fourth-generation selective progestin that has a significant local effect on endometriotic lesions, has little androgenic, less estrogenic, low glucocorticoid or mineralocorticoid activity and minimal effect on metabolic parameters, and is used in the medical treatment of endometriosis. However, there is no data on the effects of hormonal therapy used in the treatment of endometriosis on the frequency and severity of symptoms of fibromyalgia associated with endometriosis. Therefore, in this study, it was aimed to evaluate the effects of progesterone therapy used in endometriosis patients on fibromyalgia frequency, fibromyalgia severity and quality of life.
Endometriosis usually occurs during the reproductive period of women and poses a significant burden on quality of life and social costs. The estimated prevalence in premenopausal women is 10% in clinical studies and the frequency rises to 50% in symptomatic patients with pelvic pain and infertility. Observational studies in Europe estimated the prevalence to be 8-15 per 1000 people.~Fibromyalgia is a common musculoskeletal chronic painful condition that may be accompanied by cognitive impairment, somatic symptoms, fatigue, and psychiatric symptoms. The population frequency is given as 20-80 per 1000 people. Fibromyalgia is most often diagnosed in women aged 20-55 years; prevalence increases with age and is associated with a higher prevalence of comorbidities, including endocrine and genitourinary disorders. Co-existance of endometriosis and fibromyalgia is a special entity that has not been enlightened in detal yet.