Cortisol Calculator

Normal range: 6-23 mcg/dL

Normal range: 3-16 mcg/dL (helps assess diurnal variation)

Normal range: 10-60 pg/mL (critical for diagnosis)

Normal range: 10-100 mcg/day

When should cortisol and ACTH be tested?

Testing is indicated for symptoms of cortisol excess (weight gain, easy bruising, muscle weakness, hypertension) or deficiency (fatigue, weight loss, low blood pressure, salt craving). ACTH should always be measured simultaneously with cortisol for diagnostic interpretation. Timing is critical: morning cortisol (8 AM) is best for screening adrenal insufficiency, while late-night cortisol helps diagnose Cushing syndrome.

What is the difference between Cushing syndrome and Cushing disease?

Cushing syndrome is the general term for any condition causing excess cortisol exposure. Cushing disease specifically refers to a pituitary adenoma secreting excess ACTH, which is the most common endogenous cause (60-70% of cases). Other causes of Cushing syndrome include adrenal tumors (ACTH-independent), ectopic ACTH production from tumors like small cell lung cancer, and exogenous glucocorticoid use.

How is a random cortisol level interpreted?

Random cortisol levels are difficult to interpret due to normal diurnal variation and stress-induced elevation. A morning cortisol < 3 mcg/dL strongly suggests adrenal insufficiency, while > 18 mcg/dL makes it unlikely. Values between 3-18 mcg/dL require ACTH stimulation testing. For Cushing syndrome, random levels are less useful; 24-hour urine free cortisol, late-night salivary cortisol, or dexamethasone suppression tests are preferred.

What is an ACTH stimulation test?

The ACTH stimulation (cosyntropin) test evaluates the adrenal glands' ability to produce cortisol in response to synthetic ACTH. After measuring baseline cortisol and ACTH, 250 mcg of cosyntropin is given IV or IM. Cortisol is measured at 30 and 60 minutes. A peak cortisol ≥ 18-20 mcg/dL is normal. Inadequate response indicates adrenal insufficiency, though it cannot distinguish primary from secondary causes without baseline ACTH measurement.

Can medications affect cortisol testing?

Yes, many medications affect cortisol. Exogenous glucocorticoids (prednisone, dexamethasone, hydrocortisone, inhaled or topical steroids) suppress the HPA axis and can cause iatrogenic Cushing syndrome or adrenal suppression. Oral contraceptives and estrogen increase cortisol-binding globulin, elevating total cortisol (free cortisol remains normal). Phenytoin, rifampin, and other enzyme inducers accelerate cortisol metabolism. Always inform your doctor of all medications before testing.

What is adrenal crisis and how is it treated?

Adrenal crisis is a life-threatening emergency occurring in patients with adrenal insufficiency during severe stress, illness, or if glucocorticoid replacement is missed. Symptoms include severe weakness, confusion, abdominal pain, vomiting, severe hypotension, and shock. Treatment requires immediate IV hydrocortisone 100 mg followed by continuous infusion, aggressive IV fluids, and treatment of precipitating cause. All patients with adrenal insufficiency should wear medical alert identification and have injectable hydrocortisone available.

How is the 24-hour urine free cortisol test performed?

The patient collects all urine over a 24-hour period in a special container, usually starting with the second morning void and ending with the first void the next morning. The collection must be complete and refrigerated. The laboratory measures total cortisol excreted and creatinine to verify adequate collection. Values > 100 mcg/day (or 3-4 times the upper limit) suggest Cushing syndrome. This test is less affected by stress than serum cortisol but can be falsely elevated with high fluid intake.

What is ectopic ACTH syndrome?

Ectopic ACTH syndrome occurs when non-pituitary tumors produce ACTH, causing Cushing syndrome. Small cell lung cancer is the most common cause, but carcinoid tumors, medullary thyroid cancer, and pheochromocytomas can also produce ACTH. These patients typically have very high ACTH and cortisol levels, severe hypokalemia, rapid symptom onset, and may have hyperpigmentation. Imaging of chest, abdomen, and pelvis is needed to locate the tumor. Treatment focuses on tumor removal or control.