title: Cortisol secretion after adrenocorticotrophin (ACTH) and dexamethasone tests in healthy female and male dogs.
abstract: BACKGROUND
  For the conclusive diagnosis of Cushing's Syndrome, a stimulating ACTH test or a low suppressive Dexamethasone test is used. Reports in other species than the dog indicate that plasma cortisol concentration after ACTH administration is affected by gender. We investigated the effect of gender on the cortisol response to ACTH and Dexamethasone tests in dogs.
  
  
  METHODS
  Seven healthy adult Cocker Spaniels (4 females and 3 males) were assigned to a two by two factorial design: 4 dogs (2 females and 2 males) received IV Dexamethasone 0.01 mg/kg, while the other 3 dogs received an IV saline solution (control group). Two weeks later the treatments were reversed. After one month, ACTH was given IV (250 microg/animal) to 4 dogs (2 female and 2 males) while the rest was treated with saline solution (control group). Cortisol concentrations were determined by a direct solid-phase radioimmunoassay and cholesterol and triglycerides by commercial kits.
  
  
  CONCLUSIONS
  No effect of treatment was observed in metabolite concentrations, but females presented higher cholesterol concentrations. ACTH-treated dogs showed an increase in cortisol levels in the first hour after sampling until 3 hours post injection. Cortisol concentrations in Dexamethasone-treated dogs decreased one hour post injection and remained low for 3 hours, thereafter cortisol concentrations increased. The increase in cortisol levels from one to two hours post ACTH injection was significantly higher in females than males. In Dexamethasone-treated males cortisol levels decreased one hour post injection up to 3 hours; in females the decrease was more pronounced and prolonged, up to 5 hours post injection.
  
  
  CONCLUSIONS
  We have demonstrated that cortisol response to ACTH and Dexamethasone treatment in dogs differs according to sex.
authors.affiliation: Laboratorio de Técnicas Nucleares, Facultad de Veterinaria, Montevideo, Uruguay. ppessina@hotmail.com
authors.forename: Paula
authors.initials: P
authors.lastname: Pessina
authors.forename: Andrea
authors.initials: A
authors.lastname: Fernández-Foren
authors.forename: Enrique
authors.initials: E
authors.lastname: Cueto
authors.forename: Luis
authors.initials: L
authors.lastname: Delucchi
authors.forename: Victor
authors.initials: V
authors.lastname: Castillo
authors.forename: Ana
authors.initials: A
authors.lastname: Meikle
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D002784:Cholesterol / Q000097:blood; D003907:Dexamethasone / Q000494:pharmacology*; D004285:Dogs / Q000502:physiology*; D005260:Female; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism*; D008297:Male; D012737:Sex Factors; D014280:Triglycerides / Q000097:blood
chemical_list: D014280:Triglycerides; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D002784:Cholesterol; D006854:Hydrocortisone
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