Endometriosis - characteristics

Endometriosis, also referred to as adenomyosis of the uterus, is an increasingly common pathology in women of reproductive age, usually between 20 and 35 years of age. Accurately estimating the percentage of women affected by endometriosis is very difficult due to the fact that not all women develop symptoms of the disease and it is correctly diagnosed.

Despite many years of research into its pathogenesis, researchers have not yet been able to come to a clear conclusion on the causes and mechanisms of its formation. Endometriosis was discovered over 100 years ago and is still quite a mystery to researchers. Due to the unexplained causes of this pathology, both its diagnosis and its treatment cause many difficulties for medics.

Endometriosis is a condition characterised by the presence of elements histologically similar to the endometrium, outside the uterine cavity. The foci of endometriosis may appear as endometrial cysts, infiltration of the rectovaginal septum, or peritoneal implants appearing on the sacro-uterine ligaments, in the sinus of Douglas, on the surface of the ovary, the walls of the minor pelvis, and sometimes in the upper abdominal cavity and on the surface of the bowel and bladder.

During the menstrual cycle, the endometrial fragments function in a similar way to those in the uterus, undergoing hormonal changes, and during menstruation they begin to exfoliate and bleed. As the blood does not have adequate drainage, it accumulates to form clots, leading to the formation of endometrial (chocolate) cysts and inflammation. The endometrial lesions enlarge with each cycle, as well as being able to form in other places causing increasingly severe symptoms of the condition.

It is estimated that more than half of women diagnosed with endometriosis have fertility problems, but its link to infertility is still debatable and the cause-and-effect relationship is still unclear.

Endometriosis and fertility

Likely mechanisms affecting fertility in endometriosis:

• changes in the composition of the peritoneal fluid: increased fluid volume, presence of increased levels of prostaglandins, interleukin IL-1 (toxic to embryos), IL-26, IL-8, activated macrophages, proteases and tumour necrosis factor (TNF),
• ovulatory disorders due to ovarian malfunction: transient hyperprolactinaemia, abnormal development of ovarian follicles, premature rupture of ovarian follicles, luteal phase disorders, luteinisation of persistent ovarian follicles,
• fallopian tube disorders: obstruction, impaired mobility,
• immunological disorders: increased levels of IgG, IgA and lymphocyte class antibodies, presence of autoantibodies against endometrial antigens, changes in expression of homebox genes (HOXA) 10,
• impaired sexual intercourse.

Advanced endometriosis may cause significant anatomical changes of the reproductive organ, thus decreasing the efficiency of the processes leading to the release of the ovum, its fertilisation and transport. The presence of endometriosis foci often leads to chronic inflammation in the peritoneum and pelvis, which may be an indirect cause of difficulties in getting pregnant.

The inflammatory reaction occurring in the peritoneal cavity of women with endometriosis appears to be responsible for adhesions and scarring lesions, which can mechanically damage the fallopian tubes and interfere with normal ovarian function. The inflammatory environment of the pelvis, can adversely affect folliculogenesis, reduce the quality of the ovum, and impair fertilisation and embryo implantation. A change in the quantity and composition of the peritoneal fluid in women with endometriosis adversely affects sperm motility, oocyte-sperm interaction, acrosomal response, and the embryo and fallopian tube.

If endometrial lesions are located in the sinus of Douglas, a woman may experience pain during sexual intercourse. Dyspareunia is associated with foci of deeply infiltrating endometriosis in the sacro-uterine ligaments and may be the cause of limiting the frequency of sexual intercourse, thus reducing the chances of conception.