Endometriosis is driven by relatively low levels of prenatal and postnatal testosterone. Testosterone affects the developing hypothalamic–pituitary–ovarian (HPO) axis, and at low levels, it can result in an altered trajectory of reproductive and physiological phenotypes that can mediate the symptoms of endometriosis.The features of EMJ appeared similar at different stages, whereas they are statistically different if correlated with patients without endometriosis. Women with endometriosis exhibit, relative to controls: have shorter AGDs, indicative of lower prenatal testosterone (2) lower LH relative to FSH, (3) higher SHBG, (4) higher serum oxytocin, (5) lower ovarian and serum testosterone, (6) lower AMH, (7) lower WHR and BMI, (8) lower β-endorphin and (9) a wider endometrial-myometrial junction (EMJ).
The endometrial-myometrial junctional junction (EMJ), is related to peristaltic-like movements in the non-pregnant uterus. Hyperperistalsis and dysperistalsis of uterus underlie many important disorders such as dysmenorrhea, infertility, endometriosis, implantation failure and preterm birth. The maximum thickness of EMJ in patients with endometriosis is significantly greater than in patients without endometriosis (6.5 ± 1.9 mm vs 4.8 ± 1.0 mm. The features of EMJ appeared similar at different stages, whereas they are statistically different if correlated with patients without endometriosis.
The major proteins for uterine contraction of the non-pregnant uterus are Oxytocin (OT) and the oxytocin receptor (OTR). The expression level of OTR in the fundus region of the EMJ is positively associated with the severity of dysmenorrhea in endometriosis group (r = 0.870, p < 0.05). Comparing to normal uteri, the expression of OTR in the secretory phase was significantly higher in the endometriosis uteri (p < 0.05). In the fundus of endometriosis uteri, OTR expression was significantly higher in both the proliferative and secretory phases (p = 0.045 and 0.028, respectively).
Given the critical role oxytocin receptors and the increased thickness of the EMJ in women with endometriosis it is not surprising that oxytocin antagonists such as atosiban are effective in improving implantation rates and are helpful in the treatment of PTL.
A total of 180 women undergoing intracytoplasmic sperm injection who had top-quality embryos were randomly allocated into treatment and control groups. All the patients had infertility due to tubal factor, hormonal-anovulatory disorders, male factor or unexplained reasons. The treatment group received intravenous administration of atosiban before embryo transfer with a total administered dose of 37.5 mg. In the control group, the same number of cycles was performed with placebo medication. The clinical pregnancy rate (PR) per cycle and implantation rate (IR) per transfer were 46.7% and 20.4% in the atosiban-treated group, which were significantly higher than in the control group (28.9% and 12.6%, respec tively, P = 0.01). The miscarriage rates of groups 1 and 2 were 16.7% and 24.4%, respectively (P = 0.01). These results have indicated that atosiban increases the IR and PR after IVF–embryo transfer.
In a second study of 120 women, atosiban, was given before transfer of frozen-thawed embryo to women with endometriosis. Serum OT level (1.89 ± 0.33 vs. 1.66 ± 0.32 ng/L), PGF2α (2.83 ± 0.34 vs. 2.36 ± 0.35 ng/L) level, and uterine contractions (2.5 ± 1.2 vs. 1.8 ± 1.0 waves per minute) in the endometriosis group were all significantly higher than in the tubal factor group. The clinical pregnancy rate per cycle and implantation rate per transfer were 58.3% and 41.0%, respectively, in the atosiban treatment group, significantly higher than in the control group (38.3% and 23.4%, respectively). Women with endometriosis showed higher serum OT level, PGF2α level, and uterine contractions. Atosiban treatment before ET in endometriosis is effective in the priming of the uterus, suitable for embryo implantation.