A cortisol test measures the level of cortisol, a steroid hormone produced by the adrenal glands, in the blood, urine, or saliva. Cortisol plays a crucial role in regulating various body functions, including metabolism, immune response, and stress management. This test is commonly used to diagnose conditions related to abnormal cortisol levels, such as Cushing's syndrome or Addison's disease.
Cortisol levels naturally fluctuate throughout the day, typically peaking in the early morning and declining in the evening. Because of this diurnal variation, the timing of the cortisol test is important. Blood or saliva samples are often collected in the morning and late afternoon to provide a comprehensive view of cortisol production.
The cortisol test can help identify hypercortisolism, a condition characterized by excessively high cortisol levels, which may indicate Cushing's syndrome. Symptoms of Cushing's syndrome include weight gain, high blood pressure, and changes in skin appearance. Conversely, low cortisol levels may point to Addison's disease, where the adrenal glands produce insufficient hormones. Symptoms of Addison's disease include fatigue, weight loss, and low blood pressure.
In some cases, a 24-hour urine cortisol test is performed to measure the total cortisol excreted over a day, providing additional information on adrenal gland function. Saliva tests are also gaining popularity due to their convenience and non-invasive nature.