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Feline Adrenal and Pituitary Function Tests

Low Dose Dexamethasone-Suppression Test

This is a useful screening test for feline hyperadrenocorticism (Cushing’s syndrome).
Note: The dexamethasone dose is higher than that used for low dose testing in dogs.

  1. Draw a baseline blood sample in a plain red-top tube for serum.
  2. Inject 0.1 mg/kg of dexamethasone sodium phosphate intravenously.
  3. Collect additional blood samples 4 and 8 hours later.
  4. Follow the sample processing directions in ACTH-Response Test (below), Steps 4 to 8. Note:  Do not use serum separator tubes as these gels/clot activators can falsely elevate results.

High Dose Dexamethasone-Suppression Test

This test may help discriminate between pituitary dependent hyperadrenocorticism and adrenal tumor(s).

  1. Draw a baseline blood sample in a plain red-top tube for serum.
  2. Inject 1.0 mg/kg of dexamethasone sodium phosphate intravenously.
  3. Collect additional blood samples 4 and 8 hours later.
  4. Follow the sample processing directions in ACTH-Response Test (below), Steps 4 to 8. Note: Do not use serum separator tubes as these gels/clot activators can falsely elevate results.

ACTH-Response Test

This test should be used to evaluate adrenocortical function after treatment for hyperadrenocorticism (Cushing’s syndrome) and to diagnose iatrogenic Cushing’s syndrome. It is a poor test for diagnosis of hyperadrenocorticism.

  1. Draw a baseline blood sample in a plain red-top tube for serum.
  2. Inject 0.125 mg of Cortrosyn® intramuscularly or 5 ug/kg Cortrosyn® intravenously or inject 2.2 IU/kg of ACTH Gel intramuscularly.
  3. Collect additional blood sample(s) 1 hour  later for Cortrosyn® or 1 and 2 hours for ACTH Gel.
  4. Allow blood sample to clot – this may take place at room temperature for 60 minutes or in the refrigerator over 2-4 hours.
  5. Centrifuge samples at a speed and time that allow for adequate separation and specimen yield.
  6. After centrifugation, draw off serum and transfer to another tube suitable for shipping and/or frozen storage.
  7. Frozen storage is recommended for samples if time before shipping will be 12 hours or more.
  8. Optimally, ship samples frozen with cold packs so they arrive partially thawed or chilled. Frozen samples are not required.
    Note: Do not use serum separator tubes as these gels/clot activators can falsely elevate results.

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