Note: These protocols are not suitable for horses.
After establishing a presumptive diagnosis of either HYPERADRENOCORTICISM or HYPOADRENOCORTICISM in a dog based on clinical signs, physical examination, serum biochemistry, haematology and urinalysis, dynamic screening tests are often the next step in the diagnostic work-up.
- The two most common tests used in the diagnosis of hyperadrenocorticism are the Low Dose Dexamethasone Suppression Test (LDDST) and ACTH Stimulation Test.
- The LDDST is recommended for evaluation of endogenous hyperadrenocorticism, although the ACTH stimulation test may also be used.
- The ACTH stimulation test is essential for testing for iatrogenic hyperadrenocorticism.
- The ACTH stimulation test is used for monitoring the response to treatment of hyperadrenocorticism with Lysodren (mitotane).
The ACTH stimulation test is the only test that can be used to confirm a diagnosis of hypoadrenocorticism.
TESTS OF ADRENAL FUNCTION
There are numerous protocols and tests advocated in differing texts, but the following protocols are used commonly:
LDDST (Low Dose Dexamethasone Suppression Test)
- Collect a baseline serum sample (0 hour) and then inject 0.01 mg/kg
- Collect another serum sample 3 or 4 hours later and again at 8 hours.
ACTH Stimulation Test
Dose: 250µg (1 vial) per dog OR 5µg/kg to a maximum of 250µg per dog
Collection: Pre and 1 hour post
Synacthen ACTH DEPOT
Dose: Body weight < 15kg - 0.25 mg/dog
Body weight > 15kg - 0.5mg/dog
Collection: Pre and 2 hour post
Particularly for hyperadrenocorticism, interpretation of the results obtained must be made in the light of all the available data and one must realise that neither test is foolproof; ie. neither test is 100% sensitive and 100% specific. Some cases may require re-testing to rule in/out hyperadrenocorticism.
**Synacthen is produced by Ciba-Geigy Australia. DCI-02 Adrenal Function (V1.2, 27-05-2004)