title: Effect of conjugated equine estrogens and tamoxifen administration on thyroid gland histomorphology of the rat.
abstract: OBJECTIVE
  The aim of this study was to evaluate the action of the conjugated equine estrogens and tamoxifen on the morphology of thyroid gland in ovariectomized (OVx) rats.
  
  
  METHODS
  Conjugated equine estrogens (CEE), clinically used as estrogen therapy, is a complex formulation containing multiple estrogens that decrease menopausal symptoms. Thirty ovariectomized rats were randomly divided into 3 treatment groups: GI, vehicle (propylene glycol); GII, CEE 200 microg/kg per day; and GIII, tamoxifen 1 mg/kg per day. Another group of 10 rats with intact ovaries (GIV) was included, treated with the vehicle, and sacrificed during estrous. All animals were treated by gavage for 50 days, after which they were sacrificed. Blood samples were collected, and the thyroid was removed for morphological analysis and PCNA evaluation through immunohistochemical study.
  
  
  RESULTS
  The thyroid follicular cell height was increased in animals treated with CEE (14.90 +/- 0.20 microm), with TAM (14.90 +/- 0.10 microm), and in rats with intact ovaries (15.10 +/- 0.50 microm) in comparison to that of the vehicle group (9.90 +/- 0.20 microm) (P < 0.001). The follicular area was larger in the CEE (2,225 +/- 51 microm2) and TAM (2,127 +/- 67 microm2) groups compared to that of the vehicle group (5,016 +/- 53 microm2). The levels of T4 and T3 in rats treated with CEE, with Tamoxifen and in rats with intact ovaries, were higher than those those in the vehicle group (P < 0.001). The PCNA index in the vehicle group was lower than in other groups.
  
  
  CONCLUSIONS
  Our data suggest that estrogen and tamoxifen administration has a proliferative effect on the thyroid.
authors.affiliation: Department of Obstetrics and Gynecology, University of São Paulo Medical School, São Paulo, Brazil.
authors.forename: Luiz Felipe Bittencourt
authors.initials: LF
authors.lastname: de Araujo
authors.forename: José Maria
authors.initials: JM
authors.lastname: Soares
authors.forename: Ricardo Santos
authors.initials: RS
authors.lastname: Simões
authors.forename: Pedro Luiz
authors.initials: PL
authors.lastname: Calió
authors.forename: Ricardo Martins
authors.initials: RM
authors.lastname: Oliveira-Filho
authors.forename: Manuel de Jesus
authors.initials: Mde J
authors.lastname: Simões
authors.forename: Mauro Abi
authors.initials: MA
authors.lastname: Haidar
authors.forename: Edmund C
authors.initials: EC
authors.lastname: Baracat
mesh_terms: D000818:Animals; D004965:Estrogen Antagonists / Q000494:pharmacology*; D004966:Estrogens, Conjugated (USP) / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D005260:Female; D010052:Ovariectomy; D018809:Proliferating Cell Nuclear Antigen; D051381:Rats; D017208:Rats, Wistar; D013629:Tamoxifen / Q000494:pharmacology*; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects*; D013972:Thyrotropin / Q000097:blood / Q000187:drug effects; D013974:Thyroxine / Q000097:blood / Q000187:drug effects; D014284:Triiodothyronine / Q000097:blood / Q000187:drug effects
chemical_list: D004965:Estrogen Antagonists; D004966:Estrogens, Conjugated (USP); D018809:Proliferating Cell Nuclear Antigen; D014284:Triiodothyronine; D013629:Tamoxifen; D013972:Thyrotropin; D013974:Thyroxine