Endocrine testing

(see LabNote 56 ‘Equine PPID and EMS testing’ for a more detailed description).

i. Suspected thyroid dysfunction: total T4 (test code tt4), free T4 (test code ft4d), or as a panel including both (test code tprf1).

  • Requires 1 mL of frozen serum shipped with a freezer pack. Do not collect blood into SST collection tubes.
  • free T4 testing is batched weekly.

ii. Suspected pituitary pars intermedia dysfunction (PPID): glucose, insulin, ACTH - can be ordered individually or as a panel, test code cuin, “Equine PPID (Cushings) profile”.

  • ACTH requires 1.0 mL of EDTA plasma, which should be separated immediately following sample collection, placed into a plastic tube labelled as plasma, frozen, and shipped with a freezer pack. Do not send whole blood. Note: ACTH is very heat-labile.
  • For insulin and glucose, collect blood into a red-top vacutainer (do not use SST blood collection tubes), avoiding hemolysis. Allow the sample to clot, and then centrifuge. Transfer the serum into a leakproof tube labelled as serum. Refrigerate or freeze, and ship with freezer packs.
  • 1.5 mL of serum is required for insulin and glucose.
  • Insulin testing is batched weekly.

iii. Suspected equine metabolic syndrome (EMS): glucose, insulin - can be ordered individually or as a panel, test code insgluc, “insulin and glucose”.

  • Collect blood into a red-top vacutainer (do not use SST blood collection tubes), avoiding hemolysis. Allow the sample to clot, and then centrifuge. Transfer the serum into a leakproof tube labelled as serum. Refrigerate or freeze, and ship with freezer packs.
  • 1.5 mL of serum is required for insulin and glucose.
  • Insulin testing is batched weekly.
  • Fasting is not required, but horses should not be fed grain within 4 h prior to sampling.