Today is the start of European Endometriosis Prevention and Information Week.
What is endometriosis?
- a recurrent pelvic pain, sometimes very severe, especially at the time of menstruation. This cyclical nature is suggestive of the disease. The lesions are indeed sensitive to female hormones and behave like uterine tissue. The lesions will therefore proliferate, bleed and leave fibrous scars with each menstrual cycle. In some patients, significant innervation of the lesions may contribute to the extreme pain sometimes experienced.
- pain during sexual intercourse (dyspareunia) or during defecation or urination.
The disease can also be totally asymptomatic. In this case, it is usually discovered incidentally when the patient consults because of difficulty in conceiving a child. A significant proportion of endometriotic patients are indeed infertile. The scientific explanation for this link is not entirely clear. The presence of clusters of tissue, and in particular that of ovarian cysts, can create a mechanical barrier to fertilisation in the case of serious lesions. Recent studies also show that the endometrium of endometriotic patients has abnormal hormone and gene expression profiles (see below). It is therefore possible that the uterus of patients has characteristics that are unfavourable for the implantation of an embryo.
Mechanisms to be clarified
The mechanisms that lead to endometriosis are still poorly understood. However, the main hypothesis is that of the implantation of uterine material from retrograde menstruation. During menstruation, blood can pass through the fallopian tubes into the abdominal cavity, carrying with it fragments of endometrium and even pluripotent cells capable of generating new endometrial foci.
Treatment only if symptoms occur
A clinical and ultrasound examination, or even an MRI scan, can detect endometriosis. But thehe definitive diagnosis is based on the analysis of endometrial tissue taken during laparoscopy (minimally invasive surgery).
Asymptomatic, painless endometriosis which does not cause problems for fertility is generally not detected and therefore not treated. When a patient discovers her endometriosis because of pain, she is usually offered the following first-line treatment hormonal treatment intended to induce amenorrhea (continuous monophasic estrogen-progestin contraceptives, progestins, danazol or GnRH analogues), thus reducing the pain linked to the hormonal response of the endometriosis lesions. However, although this treatment masks the pain, it does not prevent the progression of the lesions, however slowly.
Surgery is the reference treatment for endometriosis because it allows the lesions to be removed as completely as possible. Thus, painful symptoms can disappear for many years, or even completely. The surgical difficulty is however amplified in the case of small disseminated lesions or when the intervention induces an unfavourable risk/benefit ratio, with for example a risk of incontinence.
Better understanding of the links between endometriosis and infertility
Researchers suspect that there is also biological and physiological differences between women with and without endometriosis, which are believed to be the cause of the reduced fertility often associated with this disease. Research conducted at the Cochin Hospital, for example, has recently shown that three of the four genes coding for prostaglandin receptors, chemical mediators of inflammation, are 10 to 20 times more expressed in the uterine endometrium of patients suffering from endometriosis than in that of women who do not have the disease. This rate is even multiplied by forty in endometrial tissue extracted from lesions. At the same time, the expression of a key enzyme in the synthesis of prostaglandins, PTGS2, is increased almost tenfold in the endometrium of endometriosis patients. Other biological avenues seem relevant to explore in order to understand the infertility of these patients, such as the function and ovarian reserve of women with endometriosis.
Several studies also point to the existence of environmental risk factors. For example, researchers are questioning the possible role of endocrine disruptors or the influence of fatty acids polyunsaturated fatty acids and other dietary components that can lead to epigenetic abnormalities. For example, a recent study in mice shows that prenatal exposure of mice to Bisphenol A may promote an endometriosis-like condition in female mice.