Collection Protocol

DOGS, CATS, and OTHER SPECIES: Collect blood in appropriate vacutainer tube. Centrifuge sample immediately. Transfer (pipette) EDTA plasma into a plain leakproof plastic tube (label as EDTA plasma). Endogenous ACTH will bind to glass. Freeze sample until shipment as increased temperature causes a false decrease in ACTH concentration.

Fasting is only necessary to avoid lipemia. If the sample is not lipemic, non-fasting is okay. If the sample is still lipemic after fasting or fasting is medically contraindicated, indicate on the submittal form and submit.

HORSES: Collect blood in appropriate vacutainer tube. Centrifuge sample within four hours of collection. Transfer (pipette) plasma into a plain leakproof plastic tube. Endogenous ACTH will bind to glass. Freeze sample until shipment as increased temperature causes a false decrease in ACTH concentration.

Unspun samples will not be accepted. Do not send whole blood.

Shipping Requirements

Freeze sample until shipment. Ship on ice via overnight courier. Sample must arrive frozen or chilled.

We recommend shipping with ice packs using the MSU VDL Insulated Mailer with UPS (99220 - single, 99221 - 3 pack, 99222 - 6 pack).

Additional Information

DOGS: Measurement of endogenous ACTH may be used to differentiate pituitary-dependent hyperadrenocorticism (PDH) from a functional adrenocortical tumor (adrenal-dependent hyperadrenocorticism); however, a definitive result may not be possible as equivocal results can occur. Interpretation is made on the premise of prior confirmation of hyperadrenocorticism by adrenal function testing (e.g., low dose dexamethasone suppression or ACTH stimulation). This test is not useful in screening for hyperadrenocorticism as there is considerable overlap of single baseline results in dogs with PDH and normal dogs.

This test may also be used for differentiation of primary versus secondary hypoadrenocorticism. Primary hypoadrenocorticism refers to destruction of adrenocortical cells with a compensatory increase of ACTH, which is the most common form in dogs. Secondary hypoadrenocorticism refers to reduced glucocorticoid production due to a lack of ACTH release. Samples should be collected before administration of corticosteroids.

HORSES: Clinical studies have shown that measurement of endogenous ACTH is useful to screen for pituitary pars intermedia dysfunction (PPID) in horses. Interpretation of results is made in reference to signalment, history, clinical signs, and physical changes consistent with PPID. There is a seasonal variation in endogenous ACTH with higher values from July to December.

In instances where a baseline endogenous ACTH is equivocal, performing a thyrotropin-releasing hormone (TRH) stimulation test for ACTH measurement may be beneficial in identification of PPID. Seasonally adjusted reference intervals have not been established for the thyrotropin-releasing hormone stimulation test from July to December. During this time period, the TRH stimulation test may only be used to identify negative cases.

Equine thyrotropin-releasing hormone (TRH) stimulation test: collect a baseline EDTA plasma sample for ACTH measurement, administer 0.5 mg (equids < 250 kg) or 1.0 mg (equids > 250 kg) of TRH intravenously, collect an EDTA plasma sample for ACTH measurement exactly 10 minutes after TRH administration.

Do not perform a thyrotropin-releasing hormone (TRH) stimulation test after an oral sugar test (OST) due to blunting of pituitary ACTH responses to TRH. Testing may be performed either following a short term fast or after hay is fed. Grain should not be fed prior to the test. Measure only ACTH response. Do not measure cortisol response.