title: Synthetic adrenocorticotropic hormone stimulation tests in healthy neonatal foals.
abstract: BACKGROUND
  Cosyntropin (adrenocorticotropic hormone [ACTH]) stimulation tests are used to evaluate adrenal function. Low-dose ACTH stimulation tests are the most accurate method for diagnosing relative adrenal insufficiency in critically ill humans but have not been evaluated in foals.
  
  
  OBJECTIVE
  Peak serum cortisol concentrations in healthy foals will not be significantly different after intravenous administration of 1, 10, 100, and 250 microg of cosyntropin.
  
  
  METHODS
  14 healthy neonatal foals, 3-4 days of age.
  
  
  METHODS
  A randomized cross-over model was used in which cosyntropin (1, 10, 100, or 250 microg) was administered intravenously on days 3 and 4 of life. Blood samples were collected before and 30, 60, 90, 120, and 150 minutes after administration of cosyntropin for determination of serum cortisol concentration.
  
  
  RESULTS
  Serum cortisol concentrations did not significantly increase after administration of 1 microg of cosyntropin. Cortisol concentration peaked 30 minutes after administration of 10 microg of cosyntropin and 90 minutes after 100 and 250 microg of cosyntropin. There was no relationship between cosyntropin dose and serum cortisol concentration at 30 minutes. Compared with the 10-microg dose, 100 and 250 microg of cosyntropin induced significantly greater cortisol concentrations at 90 minutes, at which point the 10-microg cosyntropin-dose cortisol values were indistinguishable from baseline. There was no significant difference in the area under the cortisol concentration curve between the 100- and 250-microg doses. No effect of day of testing or foal weight on peak cortisol concentration was detected.
  
  
  CONCLUSIONS
  The results of this study suggest that 10- and 100-microg doses of cosyntropin would be appropriate for evaluating adrenal function in neonatal foals.
authors.affiliation: Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA. khart@vet.uga.edu
authors.forename: Kelsey A
authors.initials: KA
authors.lastname: Hart
authors.forename: Duncan C
authors.initials: DC
authors.lastname: Ferguson
authors.forename: Gary L
authors.initials: GL
authors.lastname: Heusner
authors.forename: Michelle Henry
authors.initials: MH
authors.lastname: Barton
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D003366:Cosyntropin / Q000008:administration & dosage* / Q000494:pharmacology*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006736:Horses / Q000097:blood*; D006854:Hydrocortisone / Q000097:blood*; D008297:Male
chemical_list: D003366:Cosyntropin; D006854:Hydrocortisone