Adrenal Function

Sample Submission and Collecting Procedures

Recommended Initial Screening Tests for Cushing's Disease in Dogs, Cats, Horses.

Dogs: Low dose dexamethasone suppression, ACTH response test, combination dexamethasone suppression:ACTH response test, or urinary cortisol:creatinine ratio. Use ACTH response test or combination test if it is possible that signs of Cushing's are due to exogenous glucocorticoid therapy (iatrogenic disease.)

Cats: ACTH response test (see below).

Horses: Dexamethasone suppression, give 0.04 mg/kg (40 micrograms per kg) dexamethasone IV and collect post sample 19-24 hours later (see below).
Cortisol (as measured in adrenal function tests). Submit 1 ml of EDTA-plasma. Centrifuge and draw off plasma within 15 minutes of blood collection. If plasma collected, ship sample(s) in plastic tubes using overnight or 2nd day mail delivery, no cooling needed. If serum is collected, ship samples in an insulated container with 1-2 cool packs. **Note: a single resting or basal cortisol measurement is not recommended for assessment of adrenal function.
ACTH Response Test (see ACTH response test section in Frequency Asked Questions for more information)

Dogs: If you use ACTH gel, collect a pre sample following cortisol collection procedure and inject ACTH gel 1 IU/lb body weight IM (max dose, 40 IU). Collect a single post-ACTH sample 2 hours later. If using cortrosyn (also known as cosyntropin or synthetic ACTH) give 5 micrograms/kg IV (maximum dose 250 micrograms) and collect a single post-ACTH sample 1 hour later.

Cats: If you use ACTH gel, collect a pre sample following cortisol collection procedure and inject ACTH gel 1 IU/lb body weight IM (max dose, 40 IU). Collect two post-ACTH samples, one at 1 hour and another at 2 hours. If you use cortrosyn (also known as cosyntropin or synthetic ACTH) give 0.125 micrograms/cat IV (this is one-half of a vial) and collect a post-ACTH samples at 1 hour. If EDTA plasma collected, ship samples using overnight or 2nd day mail, no cooling required. If samples stored longer or if serum used, ship in an insulated container with frozen gel packs. Be sure samples are tightly sealed and clearly labeled.
Low Dose Dexamethasone Suppression Test (Dogs). Collect a pre dexamethasone sample for cortisol measurement. Inject dexamethasone (Azium or dexamethasone sodium phosphate) at 0.01 mg/kg IV. Dilute the dexamethasone with sterile saline if necessary so that an accurate dose can be given. Collect post-samples for cortisol at 4 and 8 hours after dexamethasone.
High Dose Dexamethasone Suppression Test (Dogs or Cats). Collect a pre dexamethasone sample for cortisol measurement. Inject dexamethasone (Azium or dexamethasone sodium phosphate) at 0.1 mg/kg IV. Collect post samples at 4 and 8 hours.
"Ultra" or "Mega" High Dose Dexamethasone Suppression Test. Inject dexamethasone (Azium or dexamethasone sodium phosphate) at 1.0 mg/kg IV. Collect post samples at 4 and 8 hours. Use this test in dogs when previous dexamethasone suppression tests using lower doses of dexamethasone did not result in suppressions in cortisol. Do not use "ultra" high dose in diabetic dogs or in dogs with persistently high resting cortiol concentrations (above 300 nmol/l).
Dexamethasone Suppression Test for Horses. Collect a pre sample sometime between 5 to 7 pm. Inject dexamethasone (Azium or dexamethasone sodium phosphate) at 40 micrograms/kg IV and collect a single post sample 15-19 hours later (8 am to noon the next day).
Combination Dexamethasone Suppression. ACTH Response Test (Dogs). Collect a pre dexamethasone sample for cortisol measurement. Inject dexamethasone at 0.1 mg/kg IV (the "high" dose). Collect a post dexamethasone sample 4 hours later. Immediately perform ACTH response test (the post dexamethasone sample serves as the pre ACTH sample). Submit the three samples for cortisol determination.
Urinary Cortisol:Creatinine Ratio. Collect urine and centrifuge to remove particulate material. Split sample into two vials (1 ml of urine per vial). Ship samples in insulated container with cool packs.
Endogenous ACTH Measurement. Note: Contact lab before submitting samples for Endogenous ACTH.Collect resting blood sample into EDTA (purple top tube). Add trasylol (enzyme inhibitor, available from us) to blood immediately at 0.1 ml trasylol per 2 ml of blood. Mix gently. Centrifuge blood immediately. Store plasma in plastic tube. Freeze sample if stored for more than 1 day prior to shipment. Pack sample frozen or cold with several frozen gel packs in an insulated container. Ship to us using overnight mail service. Things to remember: Minimum sample volume is 1 ml. Hemolysis must be avoided. If sample is medium to severely hemolyzed, collect another sample. Ship sample to us using overnight delivery. Use several frozen gel packs or better, several pounds of dry ice. Samples can be stored frozen for at least a few week. It’s better to ship early in the week.

Test	Dog	Cat	Horse	Ferret
Resting Cortisol (nmol/L)	10 - 160	10 - 110	80 - 170	14 - 80
Post-dexamethasone Cortisol (nmol/L)	<30	<35	<30	<30
Post-ACTH Cortisol (nmol/L)	220 - 560	210 - 330	220 - 410	140 - 340
Urinary Cortisol:Creatinine Ratio	0.5 - 18
Endogenous ACTH (Resting) (pg/ml)	10 - 80	5-40	5-80
Pituitary-dependent Cushings ACTH	>15
Adrenal-dependent (adrenal tumor) ACTH	<10

Normal Values - Adrenal Function Testing

Sample Submission and Collecting Procedures