True or Pseudo-Cushing's Syndrome

Study Notes

Pseudo-Cushing's syndrome can be caused by alcohol abuse, severe depression, eating disorders, and chronic illness.
It presents with similar clinical and biochemical features as true Cushing's syndrome.
The insulin tolerance test (ITT) can differentiate between true and pseudo-Cushing's states.
ITT involves administering intravenous insulin to induce hypoglycemia and stimulate cortisol release.
In true Cushing's syndrome, there will be a blunted or absent cortisol response due to excess cortisol feedback on the HPA axis.
In pseudo-Cushing's states, the HPA axis can respond to stress, and the ITT would generally show an appropriate cortisol response.
ITT is not a first-line diagnostic test for Cushing's syndrome due to potential risks.
Alternative tests, such as dexamethasone suppression test, urinary free cortisol, or salivary cortisol measurements, are performed before considering ITT.
ITT is reserved for cases where other tests are inconclusive.
Differentiating true and pseudo-Cushing's states is important for appropriate treatment.