Cortisol Suppression Test

What sample is needed for the cortisol suppression test?

1. Take fasting blood to prepare the serum.
2. A 24-hour urine sample is needed.
3. Take a baseline 24-hour urine collection for corticosteroids (urine 17-OHCS) or urinary cortisol.

What are the Indications for the cortisol suppression test?

1. This test is done to diagnose adrenal hyperfunction (Cushing’s Syndrome).
2. This also diagnoses adrenal hypofunction (Addison’s disease).

What are the precautions for the cortisol suppression test?

1. Physical and emotional stress can increase ACTH release and interfere with the interpretation of the test result.
2. Drugs that will interfere with the results are barbiturates, oral contraceptives, estrogen, Dilantin, steroids, and tetracyclines.
3. Explain the procedure to the patients.
4. Take the patient’s weight as a baseline for evaluation of the side effects of steroids.

How will you perform the rapid cortisol suppression test?

1. This test is easy and quick to perform.
2. This is used as a screening test for Cushing’s syndrome.
   1. Obtain 4 ml of fasting blood at 8 AM.
   2. Inject I/M or  I/V cortisone.
   3. Collect 5 ml of blood after 30 and 60 minutes of injection.
   4. Serum or heparinized blood can be used.
3. What is the normal value of the rapid cortisol suppression test = Nearly zero cortisol levels.

How will you perform the prolonged suppression test?

1. Obtain 24 hours of urine as a baseline sample.
2. Collect blood for baseline cortisol level.
3. Collect 24-hour urine samples daily for 6 days.
4. On day 3, give a low dose of dexamethasone by mouth (with antacid or milk).
5. On day 5, give a high dose of dexamethasone by mouth like above.
6. Keep the urine refrigerated.
7. What is the normal value of a prolonged cortisol suppression test?
   1. Low dose = >50% reduction of plasma cortisol and 17-hydroxycorticosteroid levels (17-OCHS).
   2. High dose = 50% reduction of plasma cortisol and 17-OCHS.

What is the protocol for an overnight low-dose dexamethasone suppression test?

1. One mg of dexamethasone is given at 11 PM by mouth.
2. Collect the blood at 8 AM.
3. A normal person’s cortisol concentration is suppressed to 2  µg/dL or less.
4. Cushing’s patient does not show suppression, and the level may be >10  µg/dL.

How will you interpret the cortisol suppression test?

1. Suppression occurs in patients with:
   1. Cushing’s syndrome, where the level is >10 µg/dL.
   2. In 50% of the cases, the cause is endogenous.
2. There is no suppression in patients with:
   1. Adrenal Adenoma.
   2. Adrenal carcinoma.
   3. In the case of an ectopic ACTH-producing neoplasm.
3. Absent or failure response to cortisol stimulation is seen in:
   1. Addison’s disease (adrenal insufficiency).
   2. Hypopituitarism (secondary adrenal insufficiency).
   3. Adrenal adenoma and carcinoma.
4. Responding to cortisol stimulation indicates adrenal hyperplasia (Cushing’s syndrome).

What is the relation of Cushing’s syndrome to the dose of cortisone?

What are the causes of Adrenal hyperfunction?

1. Cushing’s Syndrome.
2. Ectopic ACTH-producing tumors
3. Adrenal adenoma or carcinoma.
4. Bilateral adrenal hyperplasia.
5. Mental depression.

What are the causes of Adrenal Hypofunction?

1. Addison’s disease.
2. Neoplastic infiltration.
3. Granulomatous inflammation, such as TB, histoplasmosis, and sarcoidosis.
4. After adrenalectomy.

How will you differentiate adrenal gland tumors?

Supp = suppression.
H.D. = high dose.

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