title: The combination of letrozole and melatonin causes regression in size not histopathological scores on endometriosis in an experimental rat model.
abstract: OBJECTIVE
  To determine the effects of the combination of letrozole and melatonin on surgically induced endometriosis.
  
  
  METHODS
  This prospective, randomized, controlled, experimental study was carried out at Yeditepe University Experimental Research Center (YUDETAM). Female non-pregnant, 17 nulligravid Wistar - Hannover albino rats with surgically induced endometriosis were used in this study. Endometriosis was induced by using homologous uterine horn transplantation in the rats. Four operations were performed on each rat. The induction of endometriosis was performed in the first operation. After two weeks of estradiol treatment the second operation was performed and endometriotic lesions were evaluated. Estrogen was then discontinued and in the study groups medications were started. During two weeks the rats were given medications and the third operation was performed for the assessment of the effects of the medications on the endometriotic foci. Then all the medications were stopped and estrogen was started again. Two weeks later all the rats were euthanized and recurrence of endometriosis was evaluated.
  
  
  RESULTS
  The sum of the lesion volumes in the control group was 93.6±31.7 mm(3) at the end of the second week. After the cessation of estradiol it decreased to 85.0±23.8 mm(3) (P=0.31) and increased to 119.7±29.4 mm(3) at the sixth week (P=0.02). A significant reduction in histopathologic scores were seen after cessation of the estradiol (p=0.04). At the end of the sixth week, histopathological scores reached the pretreatment values. In the letrozole and melatonin group the sum of the lesion volumes decreased significantly after the treatment (82.8±21.0 mm(3) and 15.7±8.0 mm(3) respectively). At the end of the sixth week, the mean volume was calculated as 43.9±31.8 mm(3) (p=0.002). Histopathologic scores were 2.3±0.1, 2.0±0.2 and 2.2±0.3 at the end of the second, fourth and sixth weeks, respectively, in the letrozole and melatonin group.
  
  
  CONCLUSIONS
  Letrozole and melatonin caused a significant regression in lesion volumes; however, histopathological scores of endometriotic lesions did not change significantly.
authors.affiliation: Yeditepe University Hospital, Department of Obstetrics, and Gynecology, Istanbul, Turkey.
authors.forename: Gazi
authors.initials: G
authors.lastname: Yıldırım
authors.affiliation: Yeditepe University Hospital, Department of Obstetrics, and Gynecology, Istanbul, Turkey.
authors.forename: Rukset
authors.initials: R
authors.lastname: Attar
authors.affiliation: Yeditepe University Hospital, Center For Reproductive Medicine, Head of The Department of Obstetrics, and Gynecology, Istanbul, Turkey.
authors.forename: Cem
authors.initials: C
authors.lastname: Fıçıcıoğlu
authors.affiliation: Yeditepe University Hospital, Department of Obstetrics, and Gynecology, Istanbul, Turkey.
authors.forename: Ateş
authors.initials: A
authors.lastname: Karateke
authors.affiliation: Yeditepe University Hospital, Department of Pathology, Istanbul, Turkey.
authors.forename: Ferda
authors.initials: F
authors.lastname: Ozkan
authors.affiliation: Yeditepe University Hospital, Department of Physiology, Istanbul, Turkey.
authors.forename: Ertuğrul
authors.initials: E
authors.lastname: Kılıç
authors.affiliation: Yeditepe University Hospital, Head of The Department of Physiology and The Director of Yeditepe University Experimental Research Center (YUDETAM).
authors.forename: Bayram
authors.initials: B
authors.lastname: Yılmaz
authors.affiliation: Yeditepe University Hospital, Department of Obstetrics, and Gynecology, Istanbul, Turkey.
authors.forename: Narter
authors.initials: N
authors.lastname: Yeşildağlar
keywords: Endometriosis; letrozole; melatonin; rat endometriosis