title: Experimental study on relationship between exogenous estrogen and breast cancer risk.
abstract: OBJECTIVE
  To investigate the relationship between exogenous estrogen and breast cancer risk.
  
  
  METHODS
  Female rats were randomly divided into three groups, namely diethylstilbestrol (DES), norethindrone compositae (CoNET) and control group. The histological structure and ultrastructural changes of mammae were observed. The levels of sexual hormones in serum were determined and the AgNOR counts, DNA contents and steroid receptor contents in mammary epithelium were also detected.
  
  
  RESULTS
  In DES group, the level of progesterone (10.38 ng/ml) was obviously lower than that in the control group (13.37 ng/ml); the incidence of hyperplasia of mammary gland (73.33%) was significantly higher than that in the control group (7.69%); and the degree of hyperplasia was obviously more serious than that in the control group. Moreover, there were 13.33% of rats with atypical hyperplasia in DES group. The DNA contents, AgNOR counts and estrogen receptor (ER) positive rate were markedly higher in DES group (95.60, 2.43 and 71.71% respectively) than in the control group (83.07, 1.88 and 40% respectively). However, in CoNET group, there were no obvious influences on ER, AgNOR and DNA in mammary epithelium.
  
  
  CONCLUSIONS
  Exogenous estrogen (DES) could affect the levels of sexual hormones in serum, accelerate the DNA duplication, increase the AgNOR counts and ER contents, and induce atypical hyperplasia and ultrastructural changes of mammary gland, hence becoming a latent risk factor of breast cancer. However, the results failed to suggest that the contraceptive, CoNET, could increase the risk of breast cancer.
authors.affiliation: Department of General Surgery, First Affiliated Hospital of Chongqing University of Medical Sciences, China.
authors.forename: X
authors.initials: X
authors.lastname: Zeng
authors.forename: Z
authors.initials: Z
authors.lastname: Yao
mesh_terms: D000818:Animals; D003280:Contraceptives, Oral, Synthetic / Q000009:adverse effects*; D003283:Contraceptives, Postcoital, Synthetic / Q000009:adverse effects*; D004054:Diethylstilbestrol / Q000009:adverse effects*; D005260:Female; D006965:Hyperplasia; D008321:Mammary Glands, Animal / Q000648:ultrastructure; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced* / Q000473:pathology; D009640:Norethindrone / Q000009:adverse effects*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D011960:Receptors, Estrogen / Q000378:metabolism; D012307:Risk Factors
chemical_list: D003280:Contraceptives, Oral, Synthetic; D003283:Contraceptives, Postcoital, Synthetic; D011960:Receptors, Estrogen; D004054:Diethylstilbestrol; D009640:Norethindrone