title: Validation of a low-dose adrenocorticotropic hormone stimulation test in healthy neonatal foals.
abstract: OBJECTIVE
  To determine the lowest ACTH dose that would induce a significant increase in serum cortisol concentration and identify the time to peak cortisol concentration in healthy neonatal foals.
  
  
  METHODS
  Prospective randomized crossover study.
  
  
  METHODS
  11 healthy neonatal foals.
  
  
  METHODS
  Saline (0.9% NaCl) solution or 1 of 4 doses (0.02, 0.1, 0.25, and 0.5 μg/kg [0.009, 0.045, 0.114, and 0.227 μg/lb]) of cosyntropin (synthetic ACTH) was administered IV. Serum cortisol concentrations were measured before and 10, 20, 30, 60, 90, 120, 180, and 240 minutes after administration of cosyntropin or saline solution; CBCs were performed before and 30, 60, 120, and 240 minutes after administration.
  
  
  RESULTS
  Serum cortisol concentration was significantly increased, compared with baseline, by 10 minutes after cosyntropin administration at doses of 0.1, 0.25, and 0.5 μg/kg. Serum cortisol concentration peaked 20 minutes after administration of cosyntropin at doses of 0.02, 0.1, and 0.25 μg/kg, with peak concentrations 1.7, 2.0, and 1.9 times the baseline concentration, respectively. Serum cortisol concentration peaked 30 minutes after cosyntropin administration at a dose of 0.5 μg/kg, with peak concentration 2.2 times the baseline concentration. No significant differences were detected among peak serum cortisol concentrations obtained with cosyntropin administration at doses of 0.25 and 0.5 μg/kg. Cosyntropin administration significantly affected the lymphocyte count and the neutrophil-to-lymphocyte ratio.
  
  
  CONCLUSIONS
  Results suggested that in healthy neonatal foals, the lowest dose of cosyntropin to result in significant adrenal gland stimulation was 0.25 μg/kg, with peak cortisol concentration 20 minutes after cosyntropin administration.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA. stewaaj@auburn.edu
authors.forename: Allison J
authors.initials: AJ
authors.lastname: Stewart
authors.forename: James C
authors.initials: JC
authors.lastname: Wright
authors.forename: Ellen N
authors.initials: EN
authors.lastname: Behrend
authors.forename: Linda G
authors.initials: LG
authors.lastname: Martin
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Kemppainen
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Busch
mesh_terms: D000224:Addison Disease / Q000097:blood / Q000175:diagnosis / Q000662:veterinary*; D000818:Animals; D000831:Animals, Newborn; D003366:Cosyntropin / Q000097:blood / Q000378:metabolism / Q000494:pharmacology*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006734:Horse Diseases / Q000097:blood / Q000175:diagnosis* / Q000378:metabolism; D006736:Horses; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D003366:Cosyntropin; D006854:Hydrocortisone