Cortisol testing is usually ordered to check for problems with the adrenal glands or the pituitary gland, because cortisol is a hormone produced and regulated by these glands. Thus, when there is a change in normal cortisol values it is normal for there to be a change in any of the glands. Using this test it is possible to diagnose diseases such as Cushing's Syndrome, in the case of high cortisol or Addison's Disease, in the case of low cortisol, for example.
Cortisol is a hormone that helps to control stress, decrease inflammation, improve the functioning of the immune system and assist the metabolism of proteins, fats and carbohydrates, keeping blood sugar levels constant. Understand what the hormone cortisol is and what it is for.
There are 3 different types of cortisol tests, which include:
- Examination of salivary cortisol: assesses the amount of cortisol in saliva, helping to diagnose chronic stress or diabetes; Examination of urinary cortisol: measures the amount of free cortisol in the urine, and a urine sample must be taken for 24 hours; Blood cortisol test: evaluates the amount of protein cortisol and free cortisol in the blood, helping to diagnose Cushing's Syndrome, for example - learn more about Cushing's Syndrome and how treatment is done.
The concentration of cortisol in the body varies during the day, which is why two collections are usually made: one between 7 and 10 am, called the basal cortisol test or 8 hours cortisol test, and the other at 4 pm, called the cortisol test 16 hours, and is usually performed when excess hormone is suspected in the body.
How to prepare for the cortisol exam
Preparing for the cortisol test is especially important in cases where it is necessary to take a blood sample. In such cases, it is recommended:
- Fast for 4 hours before collection, either at 8 or 16 hours; Avoid physical exercise the day before the exam; Rest for 30 minutes before the exam.
In addition, in any type of cortisol test, you must inform the doctor about the medications you are taking, especially in the case of corticosteroids, such as dexamethasone, as they can cause changes in the results.
In the case of salivary cortisol examination, saliva collection should preferably be done within 2 hours after waking up. However, if it is done after a main meal, wait 3 hours and avoid brushing your teeth during this period.
Reference values
The reference values for cortisol vary according to the material collected and the laboratory where the test was performed, which may be:
| Material | Reference values |
| Urine |
Men: less than 60 µg / day Women: less than 45 µg / day |
| Spittle |
Between 6 am and 10 am: less than 0.75 µg / mL Between 16h and 20h: less than 0.24 µg / mL |
| Blood |
Morning: 8.7 to 22 µg / dL Afternoon: less than 10 µg / dL |
Changes in blood cortisol values may indicate health problems, such as a pituitary tumor, Addison's disease or Cushing's syndrome, for example, in which cortisol is elevated. See what are the main causes of high cortisol and how to treat it.
Changes in cortisol results
The results of the cortisol test may be altered due to heat, cold, infections, excessive exercise, obesity, pregnancy or stress, and may not be indicative of illness. Thus, when the test result is changed, it may be necessary to repeat the test to see if any factors interfered.
