الفهرس 
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Abstract
Background: Endometriosis is an estrogen-dependent disease affecting up to 10% of women of reproductive age. It is diagnosed in 71% to 87% of females with chronic pelvic pain and in 30% of women with infertility. Letrozole is a third-generation aromatase inhibitor, suppressing local and systematical estrogen production, which plays a critical role in the pathogenesis of endometriosis and could be used as a treatment modality to avoid surgery.
Aim: The aim of this study was to investigate whether letrozole has an inhibitory effect on the growth and angiogenesis of endometriosis in an experimental rat model.
Materials and method: Twenty female, non-pregnant Wistar albino rats were used to create a model for the experimental induction of endometriosis. Rats were divided into treatment (letrozole) and control groups, endometriosis was surgically induced in rats by transplanting an autologous fragment of endometrial tissue onto the inner surface of the abdominal wall. After 30 days, rats underwent a second laparotomy to examine the endometrial implants for size and viability. The rats in the letrozole group (n =10) received oral letrozole crushed and suspended in normal saline through gastric tube at same time each day for 24 days. Rats in the control group (n =10) were given normal saline by the same route as letrozole group at the end of the treatment period, all rats were euthanized. Measurement of the ectopic endometriosis, Histological and immune-histopathological evaluation were conducted. Estradiol level was measured in all rats before each laparotomy.
Results: Treatment with letrozole reduced the size of the ectopic endometriosis. Levels of VEGF were mild in the treated group compared with severe levels in the control group. Also estradiol (E2) level was significantly decreased in letrozole group at third laparotomy compared with control group. We found gross and histological evidence that letrozole has inhibitory effect on the endometriotic implants through reducing the surface size of the implant and VEGF expression in the lesion at 3rd laparotomy compared to control group.
Recommendation: Aromatase inhibitors including letrozole could be one of the promising treatment modality for endometriosis. Further investigations are required to pave the way for clinical application.