Combined dexamethasone suppression and cosyntropin (synthetic ACTH) stimulation test in the dog: new approach to testing of adrenal gland function.
A combined dexamethasone suppression and cosyntropin (synthetic ACTH) stimulation test was developed in the dog so that information concerning pituitary gland (hypophysis) and adrenal gland competence could be provided in a single trial, during a short time span. Treatment of dogs with dexamethasone (0.1 mg/kg, IM) resulted in total suppression (below assay sensitivity or < 10 ng/ml) of plasma hydrocortisone (cortisol) at postinjection hour (PIH) 2 in 100% of the dogs, whereas suppression was inconsistent at PIH 1. Cosyntropin (0.5 U/kg, IV) administration to normal or dexamethasone-suppressed dogs increased plasma hydrocortisone concentration 3.5 to 4.5 times base-line values at PIH 1, which was the time of maximal effect. The combined test concept for adrenal gland function is valid, convenient (three sample collections; 3-hour period), and allows testing of adrenal gland response to dexamethasone suppression and ACTH stimulation in a single trial. The following test procedure for dogs is recommended: (i) collect base-line plasma sample (0900 hours) followed by injection of dexamethasone (0.1 mg/kg, IM); (ii) collect second plasma sample 2 hours after dexamethasone (to evaluate suppression of plasma hydrocortisone concentration) followed by the injection of cosyntropin (0.5 U/kg, IV); and (iii) collect a third plasma sample 1 hour later to evaluate plasma hydrocortisone concentration after cosyntropin stimulation.
D000311:Adrenal Glands / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000031:analogs & derivatives*; D000818:Animals; D003366:Cosyntropin / Q000008:administration & dosage; D003907:Dexamethasone / Q000008:administration & dosage; D004285:Dogs / Q000502:physiology*; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D007273:Injections, Intramuscular; D007275:Injections, Intravenous; D008297:Male; D010912:Pituitary-Adrenal Function Tests / Q000662:veterinary*
D003366:Cosyntropin; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone