Adrenal Insufficiency Diagnosis and Evaluation

Common Screening Tests for Adrenal Insufficiency

Diagnosing adrenal insufficiency is a multi-step process because the symptoms are often nonspecific. The diagnostic journey typically begins with endocrinology screening tests designed to detect whether cortisol levels are inappropriately low.

Because cortisol levels fluctuate according to a circadian rhythm (peaking in the early morning and dropping at night), timing is critical.

• Morning Cortisol Test: A blood sample is drawn between 6:00 AM and 9:00 AM. A robust level usually rules out insufficiency, while a very low level suggests it. Intermediate results require further testing.
• ACTH Plasma Level: This test is performed simultaneously with cortisol testing. It helps differentiate the type of insufficiency. High ACTH indicates the problem is in the adrenal glands (Primary), while low or normal ACTH suggests the problem is in the pituitary (Secondary).
• Electrolyte Panel: Doctors check for the classic Addisonian pattern: low sodium (hyponatremia) and high potassium (hyperkalemia), which is indicative of mineralocorticoid deficiency found in primary insufficiency.

Advanced Diagnostic Procedures

If screening tests are inconclusive or suggest a deficiency, endocrinologists proceed to dynamic testing. These tests provoke the adrenal glands to see if they can respond to a signal.

• ACTH Stimulation Test (Synacthen Test): This is the gold standard for adrenal insufficiency diagnosis. It assesses the adrenal cortex’s functional reserve.
• Insulin Tolerance Test (ITT): Considered the gold standard for secondary adrenal insufficiency. Insulin is injected to lower blood sugar. This stress should trigger the brain to release CRH and ACTH. It is more complex and carries risks, so it is used less frequently than the ACTH stimulation test.
• Metyrapone Test: Occasionally used to test the HPA axis integrity by blocking cortisol synthesis, forcing the pituitary to increase ACTH production.

What to Expect During the ACTH Stimulation Test

The ACTH stimulation test procedure is safe, quick, and usually performed in an outpatient setting.

1. Baseline Measurement: A nurse inserts an IV line and draws a baseline blood sample to measure cortisol before any medication is given.
2. Stimulation: You receive an injection of synthetic ACTH (Cosyntropin) either intravenously or into a muscle (usually the shoulder or thigh).
3. Observation: You rest for 30 to 60 minutes.
4. Response Measurement: Blood samples are drawn again at 30 minutes and 60 minutes post-injection to measure how much cortisol your adrenal glands produced in response to the potent signal.
5. Completion: The IV is removed, and you can return to daily activities immediately.