Adrenal Function Tests (Canine)

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.

HYPERADRENOCORTICISM

  • 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).

    • HYPOADRENOCORTICISM

    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)

    1. Collect a baseline serum sample (0 hour) and then inject 0.01 mg/kg
    2. Collect another serum sample 3 or 4 hours later and again at 8 hours.

    ACTH Stimulation Test

    Synacthen ACTH
    Formulation: 250µg/vial
    Dose: 250µg (1 vial) per dog OR 5µg/kg to a maximum of 250µg per dog
    Administration: Intravenously
    Collection: Pre and 1 hour post

    Synacthen ACTH DEPOT
    Formulation: 1mg/vial
    Dose: Body weight < 15kg - 0.25 mg/dog
              Body weight > 15kg - 0.5mg/dog
    Administration: Intramuscularly
    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)