Cortisol
Also called The stress hormone, serum cortisol, salivary cortisol
Cortisol is a hormone made by the adrenal glands, which sit on top of the kidneys. It helps the body respond to stress, which is why it is often called the stress hormone, and it also helps control blood sugar, metabolism, blood pressure and inflammation. Its output is set by ACTH (adrenocorticotropic hormone), released by the pituitary gland in the brain.
Cortisol follows a daily rhythm, normally highest in the morning and much lower by late afternoon, so the time of a sample matters as much as the number. It can be measured in blood, urine or saliva, and saliva samples collected at several times of day can map when levels rise and fall. Stress, exercise and many medicines shift results; the most common cause of an abnormal level is taking steroid medicines or stopping them suddenly. What a high result actually means is covered in What High Cortisol Actually Means on a Lab Report.
Why it matters after 45
"High cortisol" is often offered as an explanation for midlife weight gain, poor sleep and fatigue. The conditions a cortisol test is designed to find are specific: Cushing's syndrome, in which the body is exposed to too much cortisol (and which is rare when the body itself is the source), and Addison disease or adrenal insufficiency, in which it makes too little. Some of their symptoms, such as weight gain, muscle weakness and long-lasting fatigue, overlap with ordinary midlife complaints, which is why results are read against symptoms and timing.
Where it comes up
Related terms
References
- MedlinePlus. Cortisol Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/cortisol-test/
- MedlinePlus. Cortisol blood test. Medical Encyclopedia, U.S. National Library of Medicine. https://medlineplus.gov/ency/article/003693.htm
- National Institute of Diabetes and Digestive and Kidney Diseases. Cushing's Syndrome. https://www.niddk.nih.gov/health-information/endocrine-diseases/cushings-syndrome
Definitions here are educational and are not medical advice. They explain what a term means; the pages linked above cover what it means for you, and a clinician reviews your own results. Editorial & medical review policy · All glossary terms