Cortisol
Definition
Cortisol is a hormone produced by the adrenal glands, two small glands located on top of the kidneys. It regulates the stress response, inflammation, blood sugar and blood pressure. It can be measured in blood, urine or saliva.
Purpose
Diagnosis of conditions that cause abnormal cortisol levels:
- Cushing's syndrome, high cortisol due to steroid medications, tumors or adrenal disorders
- Addison's disease, low cortisol resulting from adrenal damage caused by autoimmune disease or infection
- Secondary adrenal insufficiency, low cortisol due to pituitary dysfunction
Results
A high level suggests Cushing's syndrome; a low level suggests Addison's disease or secondary adrenal insufficiency. However:
A cortisol test alone cannot diagnose the cause of abnormal cortisol levels.
Normal Values
Specific to the laboratory and to the time of sample collection.
Risks and Limitations
The daily rhythm (diurnal variation) is critical. Because cortisol fluctuates throughout the day, the blood sample is taken twice:
- In the morning, when cortisol is normally at its highest
- In the afternoon, around 16:00, when it is normally much lower
Other factors that affect the results: stress, exercise, pregnancy, temperature and medications.