title: Evaluation of aldosterone concentrations in dogs with hypoadrenocorticism.
abstract: BACKGROUND
  Some dogs with primary hypoadrenocorticism (HA) have normal sodium and potassium concentrations, a phenomenon called atypical Addison's disease. The assumption that the zona glomerulosa and aldosterone secretion in these dogs are normal seems widely accepted; however, aldosterone measurements are missing in most published cases.
  
  
  OBJECTIVE
  To measure aldosterone in dogs with HA with and without electrolyte abnormalities and to determine the time point of aldosterone peak concentrations during ACTH stimulation.
  
  
  METHODS
  Seventy dogs with HA, 22 dogs with diseases mimicking HA, and 19 healthy dogs.
  
  
  METHODS
  Prospective study. Blood samples were taken before and 60 minutes after injection of 250 μg ACTH in all dogs. Additional blood samples were taken 15, 30, and 45 minutes after ACTH in 7 dogs with HA and in 22 with diseases mimicking HA.
  
  
  RESULTS
  Baseline and ACTH-stimulated aldosterone was significantly lower in dogs with HA than in the other groups. Aldosterone was low or undetectable in 67/70 dogs with HA independently of sodium and potassium levels. In 3 dogs, sodium/potassium concentrations were normal; in 1 dog, sodium was normal and potassium decreased. In all 4, ACTH-stimulated aldosterone concentrations were below the detection limit of the assay. Aldosterone concentrations were not different at 30, 45, or 60 minutes after ACTH administration.
  
  
  CONCLUSIONS
  Cortisol and aldosterone secretion is compromised in dogs with HA with and without electrolyte abnormalities. The term atypical Addison's disease, used for dogs with primary HA and normal electrolytes, must be reconsidered; other mechanisms allowing normal electrolyte balance without aldosterone should be evaluated in these dogs.
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty University of Zurich, Zurich, Switzerland.
authors.forename: M E
authors.initials: ME
authors.lastname: Baumstark
authors.forename: N S
authors.initials: NS
authors.lastname: Sieber-Ruckstuhl
authors.forename: C
authors.initials: C
authors.lastname: Müller
authors.forename: M
authors.initials: M
authors.lastname: Wenger
authors.forename: F S
authors.initials: FS
authors.lastname: Boretti
authors.forename: C E
authors.initials: CE
authors.lastname: Reusch
mesh_terms: D000309:Adrenal Insufficiency / Q000503:physiopathology / Q000662:veterinary*; D000324:Adrenocorticotropic Hormone / Q000008:administration & dosage; D000450:Aldosterone / Q000097:blood*; D000818:Animals; D004283:Dog Diseases / Q000503:physiopathology*; D004285:Dogs; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D000075262:Hypoadrenocorticism, Familial; D008297:Male; D011188:Potassium / Q000097:blood; D011446:Prospective Studies; D012964:Sodium / Q000097:blood; D018709:Statistics, Nonparametric
chemical_list: D000450:Aldosterone; D000324:Adrenocorticotropic Hormone; D012964:Sodium; D011188:Potassium; D006854:Hydrocortisone
keywords: adrenal insufficiency; canine; mineralocorticoids