Background. External genital endometriosis (EGE) is a chronic, relapsing, progressive, hormone-dependent disease characterized by a benign growth of tissue outside the uterine cavity, similar in morphological structure and functions to the endometrium. The versatility of the pathogenetic mechanisms of the development of the disease, the variability of clinical symptoms, as well as the lack of a unified concept of endometriosis therapy dictate the need to find modern methods for correcting this pathology. Retinol may be one of these areas.
Objective. Determination of the retinol level of in peripheral blood and peritoneal fluid in patients with EGE, evaluation of the effectiveness of its use on the basis of surgically induced endometriosis in Wistar rats.
Methods. The main group included 38 patients with a histologically confirmed (based on laparoscopy) diagnosis of I-IV stage EGE according to the revised classification of the American Society for Reproductive Medicine (r-ASRM); mean age of patients was 31.7±4.1 years. The control group consisted of 10 patients without endometriosis who underwent diagnostic laparoscopy before entering the protocol of assisted reproductive technologies. Determination of the blood serum and peritoneal fluid vitamin A level in was carried out using Cloud-Clone Corp kits by ELISA.
Experimental model. A surgically induced model of endometriosis was performed on 21 mature female Wistar rats. The creation of the experimental model was carried out in three stages. The first stage was the modeling of the disease, the second was the confirmation of the presence of endometriosis based on laparoscopy and the assessment of the area of endometrioid heterotopias, followed by drug therapy of the disease; the third stage was the removal of animals from the experiment, the assessment of the area of endometrioid heterotopias in dynamics, and histological examination.
Results and discussion. Based on our study, it was found that patients with endometriosis have an increased blood serum vitamin A level, which significantly exceeds its level in the peritoneal fluid by 2 times, especially in the initial forms of the disease. An «artificial» increase in the level of retinol in the blood serum can be mediated by many reasons, primarily by disorders of its metabolism and changes in the retinol-binding protein 4 expression, that justifies the need for further research to study in depth the role of vitamin A in the pathogenesis of endometriosis. At the same time, the high efficiency of the use of retinol, characterized by complete resorption of endometriosis foci based on an experimental model of a surgically induced disease in Wistar rats, makes it possible to consider retinol as a promising method of treating the disease.

Keywords: endometriosis, vitamin A, experimental model, pathogenesis, therapy