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COMPANION ANIMALS:ADRENAL PROTOCOLS
Protocols are available for the following diagnostic tests.
Adrenal Function
  • CANINE/FELINE ACTH STIMULATION TEST
  • CANINE 3-STEP LOW DOSE DEXAMETHASONE SUPPRESSION TEST


    • Related protocols are available for
  • Reproductive Function
  • Monitoring Tests
  • Other Diagnostic Tests


    • Please contact the laboratory if you require further assistance or guidance on test protocol not shown.

    CANINE/FELINE ACTH STIMULATION TEST
  • for use in dogs with suspected spontaneous or iatrogenic hyperadrenocorticism (Cushing's)
  • dogs with suspected hypoadrenocorticism (Addison's)
  • monitoring response to treatment of dogs on triolstane or mitotane therapy
  • cats with suspected iatrogenic hyperadrenocorticism. In rare cases where spontaneous disease is suspected a combined ACTH response/dexamethasone suppression test is recommended in cats – please contact the laboratory for details.
    Protocol
  • Collect a basal sample of 2ml clotted or heparin blood - take 4 - 6 hours post tablet for trilostane monitoring.
  • Inject 0.125 mg (cats & dogs <4.0 kg) to 0.25mg (cats & dogs >4.0 kg) synthetic ACTH (Synacthen) i/v (or i/m).
  • Collect a second sample of 2ml clotted or heparin blood 1 hour post ACTH injection.
  • Separate serum/plasma if possible, label samples "pre" and "post ACTH" and dispatch to the laboratory.
    • Interpretation: Canine
    Normal basal range (30 to 240 nmol/l) rising to concentrations greater than 170 nmol/l but less than 605 nmol/l one to two hours after administration of ACTH. A cortisol level >605 nmol/l is considered positive for hyperadrenocorticism.

    This test will identify 85% of dogs with pituitary dependent hyperadrenocorticism and >50% of dogs with adrenal dependent hyperadrenocorticism.

    A low dose dexamethasone suppression test may help to distinguish between the two. It is also possible to check endogenous ACTH levels but special sampling conditions apply.

    Interpretation: Feline
    Reference range (basal cortisol) 12 - 253 nmol/l. In a normal cat, cortisol levels will increase up to 400 nmol/l post ACTH stimulation. An increase greater than this is consistent with hyperadrenocorticism.
    Note
    Synacthen (Alliance Pharmaceuticals) is not licensed for use in dogs ot cats.

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    CANINE 3-STEP LOW DOSE DEXAMETHASONE SUPPRESSION TEST
     For use in dogs with suspected spontaneous hyperadrenocorticism (Cushing's), is helpful in a proportion of cases to distinguish between pituitary and adrenal dependent HAC.
    Protocol
  • Collect a basal sample of 2ml clotted or heparin blood (preferably between 9.00 a.m. and 10.00 a.m.).
  • Inject 0.01mg/kg dexamethasone i/v.
  • Take further blood samples 3 and 8 hours post dexamethasone.
  • Separate off plasma/serum if possible and label samples clearly prior to dispatch to laboratory.
    • Interpretation
    In normal dogs, cortisol will be suppressed to <50% of the basal concentration at 3 hours and to <40nmol/l at 8 hours post injection of 0.01 mg/kg dexamethasone. Cortisol concentrations >40 nmol/l at 8 hours post dexamethasone ('escape' from suppression) are considered positive for hyperadrenocorticism.

    Where cortisol levels are suppressed at 3 hours followed by escape at 8 hours post dexamethasone, the cause is likely to be pituitary in origin. If there is no suppression the cause may be pituitary or an adrenal tumour. In that case ultrasound scanning or measurement of endogenous ACTH are recommended to distinguish between the two.

    This sensitive test will identify 90-95% of dogs with pituitary dependent hyperadrenocorticism and 100% of dogs with adrenal tumours.

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