Cortisol is an important hormone that can be measured in saliva or urine. It is a test for conditions like Cushing’s syndrome and adrenal fatigue. It can also be used to evaluate the hypothalamic pituitary axis for circadian dysregulation.
Saliva cortisol testing is simple, painless and non-invasive. It is a great choice for behavioral neuroscience students who want to study glucocorticoid regulation but do not wish to work with animals.
How it’s done
The test checks for a hormone called cortisol. Cortisol helps control protein, lipid, and carbohydrate metabolism, blood pressure, and immune system regulation. It also acts as a stress reliever. Only a small amount of cortisol is free and active; most is bound to proteins. A doctor may order this test to check for Cushing’s syndrome or other disorders that affect the pituitary and adrenal glands. It might also be ordered to see if someone is under extreme stress.
A cortisol test can be done using a sample of blood drawn at the doctor’s office or a saliva sample collected at home. A health care professional will give you a container and instructions on how to collect the sample. It’s best to do the test at night before going to bed, because cortisol levels are lowest between 11 p.m. and midnight. A person may need to collect multiple samples over 24 hours to get a representative result.
What it measures
Measurements of cortisol in saliva or urine provide a snapshot of hormone levels at one point in time. These levels vary throughout the day in a pattern called diurnal variation, rising early in the morning and falling during the afternoon and evening before reaching their lowest point around midnight. These measurements can help your doctor detect Cushing syndrome, a condition characterized by an excess of cortisol, and adrenal insufficiency or Addison disease, a condition characterized by a deficiency of cortisol.
For a saliva test, your healthcare provider puts a swab in your mouth to collect a sample, which is then sent to the lab. For a urinary cortisol test, your healthcare provider provides you with containers and instructions to collect all of the urine you produce over 24 hours and return it to the lab.
The most common use of late-night salivary cortisol is to screen for Cushing syndrome, and it has been shown to have high sensitivity and specificity. It also has emerging roles in assessing the role of glucocorticoid replacement therapy and in diagnosing conditions with low serum cortisol-binding globulin.
What the results mean
Your doctor can test your cortisol levels in your blood, urine or saliva. They will give you a kit and instruct you when to collect your sample. For a saliva test your doctor may ask you to collect it at night while you’re sleeping at home. For a blood test your doctor will put a needle into your arm at their office or hospital and then draw a small amount of blood into a tube.
The results from the Cortisol Saliva test are usually available within a few days. They will be compared to a normal cortisol level for your age group.
Only a small fraction of the cortisol in your body is free and biologically active; the majority of it is attached to protein. That’s why multiple samples of blood or saliva are typically collected at specified intervals, such as upon waking, noon, and bedtime, to assess the diurnal variation in cortisol levels. If the results are abnormal, your doctor will guide you on further evaluation and tests. These could include imaging tests of your adrenal and pituitary glands, or a dexamethasone suppression test to help determine the cause of your symptoms.
Getting a test
The cortisol test can be done through a sample of blood or urine or saliva. It’s usually done twice on the same day and analyzed at different times, because levels vary throughout the day. If the doctor wants to screen for Cushing’s disease or Addison’s disease, they may order additional tests that check for these conditions in addition to checking your cortisol levels.
For saliva testing, the doctor will give you a kit with a swab and a tube for storage. They’ll instruct you to spit into the tube at specific times of the day, usually before sleeping or eating. The doctor will also ask you to label the tube with the time of the collection, so they can track the cortisol over a period of 12 hours.
Saliva samples are simple to collect and easy to store in the home freezer. Repeated freeze-thaws don’t adversely affect the results, and this method is one of the most popular in behavioral neuroscience laboratories.
