**All cortisol test results must be interpreted in conjunction with clinical signs and other laboratory data.**

**All cortisol test results must be interpreted in conjunction with clinical signs and other laboratory data.**

1. Look at the 8-hour sample:
   1. If it is > 1.4 µg/dl it supports a diagnosis of hyperadrenocorticism. Go to step 2.
   2. If it is < 1.4 µg/dl, the test is not consistent with hyperadrenocorticism. A small percentage (5-10%) of dogs with hyperadrenocorticism have a normal LDDST. Consider testing for other diseases, doing an ACTH stimulation test, or repeating a LDDST in 1-2 months.
      Do not go on to Steps 2 and 3.
2. Look at the 4-hour sample:
   1. If it is < 1.4 µg/dl, it supports pituitary-dependent hyperadrenocorticism.
   2. If it is > 1.4 µg/dl, go to step 3.
3. Look at both the 4- and the 8-hour sample:
   1. If either of those values are less than half of the baseline, the LDDST is consistent with pituitary-dependent hyperadrenocorticism.
      1. Example: time 0 = 10.0 µg/dl; 4-hr = 2.6 µg/dl; 8-hr = 4.2 µg/dl.
      2. The 8-hr sample is > 1.4 µg/dl, so is consistent with hyperadrenocorticism, but the 4-hr sample is > 1.4 µg/dl, so based on this criterion we can't tell if it's Pituitary- or Adrenal-dependent, however...
      3. Half of the baseline would be 5 µg/dl.
      4. Both the 4-hr and 8-hr samples are less than 5 µg/dl and are therefore less than half the baseline, indicating Pituitary-dependent hyperadrenocorticism!
   2. If the 4- and 8-hour samples are more than half the baseline further evaluation is necessary to differentiate pituitary-dependent hyperadrenocorticism from an adrenal tumor. Consider one or more of the following tests:
      1. Endogenous ACTH level
      2. High dose dexamethasone suppression test.
      3. Abdominal radiographs or US

NOTE: A 2 or 6 hour sample is interpreted in the same way as a 4 hour sample.