Cortisol Test

The cortisol test, also known as the cortisol level test or serum cortisol test, is a medical laboratory test used to measure the levels of cortisol in the blood. Cortisol is a steroid hormone produced by the adrenal gland that plays a vital role in various bodily functions, including stress response, immune response, and regulation of metabolism.

Purpose of the Test

The cortisol test is typically ordered to diagnose and monitor conditions related to abnormal cortisol levels, such as:

• Cushing's syndrome: a condition caused by excess cortisol production
• Adrenal insufficiency: a condition caused by insufficient cortisol production
• Addison's disease: a condition caused by damage to the adrenal glands, leading to insufficient cortisol and aldosterone production
• Pituitary gland disorders: conditions that affect the pituitary gland, which regulates cortisol production

Types of Cortisol Tests

There are several types of cortisol tests, including:

• Serum cortisol test: measures cortisol levels in the blood
• Salivary cortisol test: measures cortisol levels in saliva
• Urine free cortisol test: measures cortisol levels in urine
• 24-hour urine test: measures cortisol levels in urine over a 24-hour period

Procedure

The procedure for a cortisol test typically involves:

• Blood sample collection: a healthcare professional will draw a blood sample from a vein in the arm
• Serum separation: the blood sample is sent to a laboratory, where the serum is separated from the other blood components
• Cortisol measurement: the cortisol level is measured using a laboratory test, such as radioimmunoassay or enzyme-linked immunosorbent assay (ELISA)

Preparation and Results

To prepare for a cortisol test:

• Avoid strenuous exercise and stress before the test
• Fasting may be required, depending on the type of test

The results of a cortisol test are typically available within a few days. Abnormal results may indicate a condition related to cortisol imbalance, and further testing or consultation with a healthcare professional may be necessary.

Reference Ranges

The reference ranges for cortisol levels vary depending on the laboratory and the type of test. Typical reference ranges are:

• Serum cortisol: 5-23 μg/dL (138-635 nmol/L) in the morning, and 2-12 μg/dL (55-331 nmol/L) in the evening
• Salivary cortisol: 0.1-0.7 μg/dL (2.8-19.3 nmol/L) in the morning, and 0.01-0.4 μg/dL (0.3-11.1 nmol/L) in the evening

Limitations and Interferences

Certain factors can interfere with cortisol test results, including:

• Certain medications, such as corticosteroids and estrogen
• Pregnancy and menstrual cycle
• Stress and exercise
• Certain medical conditions, such as liver disease and kidney disease