Cortisol to Adrenocorticotropic Hormone (ACTH) Ratio, 24-Hour Urinary Free Cortisol

Why This Test Is Done

Your doctor may order this test if you have symptoms like unexplained weight gain, high blood pressure, or unusual fatigue, or if they suspect conditions like Cushing’s syndrome (too much cortisol) or adrenal insufficiency (too little cortisol). It can also help confirm or rule out certain hormonal imbalances.

What to Expect Before the Test

You’ll collect all your urine for 24 hours, starting and ending with a sample at the same time each day. Drink plenty of water to help urine flow, but avoid caffeine or medications that may affect cortisol levels. Store samples in a refrigerator until you return them to the lab.

How the Test Works

The test measures cortisol and ACTH in your urine, which are then analyzed together to calculate the ratio. This helps determine whether your adrenal glands are producing cortisol at the right level or if there’s an imbalance.

Possible Results and Their Meaning

High cortisol-to-ACTH ratios may suggest Cushing’s syndrome, while low ratios could indicate adrenal insufficiency or other conditions affecting cortisol production. Your doctor will interpret results in the context of your symptoms and other tests.