The National Institutes of Health describes stress as a psychological response that can be both beneficial and detrimental. The American Psychological Association (APA) notes that there are different types of stress and each one has its own characteristics, symptoms, duration and treatment approaches. The three types are acute, episodic acute and chronic stress. All stress types mediate their response through the adrenal glands--particularly with the output of the hormone cortisol. All adrenal stress tests measure this parameter. However, it can be tested in different mediums.
What is Cortisol?
Cortisol is a hormone released from the adrenal gland and its release is stimulated by the production of the pituitary (brain) hormone adrenocorticotrophic hormone (ACTH). Cortisol follows a diurnal or circadian rhythm, where levels peak in the morning around 6 to 8 a.m., decrease throughout the day and are the lowest around midnight. This pattern can change with night-shift work or irregular sleep patterns. The peer-reviewed clinical lab testing website LabTestsOnline.com lists the functions of cortisol as assisting with the breakdown of macronutrients, maintaining of blood pressure and regulating the immune system. Corticol concentrations in any medium will vary in situations of infection, stress, trauma, extremes of temperature, exercise, obesity and debilitating disease.
Blood Test
Blood tests are the conventional testing medium for cortisol. It requires a blood draw that LabTestsOnline.com notes is generally requested in the early morning, when cortisol is at its peak. Generally, blood tests for cortisol are limited in that they take into consideration this single 8 a.m. sample. LabTestsOnline notes that this may be sufficient to detect decreased amounts of cortisol, but levels may not decline as they should throughout the day and this finding can be missed. Some physicians request subsequent blood draws at 4 p.m. and then again later in the evening to obtain a more comprehensive view of the diurnal pattern. Blood cortisol levels measure the bound or inactive form of the hormone.
Salivary Test
Adrenal Stress Index profiles are laboratory assessments of adrenal cortex function. According to clinical laboratories Metametrix and Diagnos-Techs, these profiles use the convenient testing medium of saliva. Because a salivary sample is as simple as spitting into a small tube, this testing strategy is considered low stress and non-invasive. Salivary hormones represent only the free, unbound and active portions of the circulating hormones. This test measures both cortisol and DHEA-S levels to detail the body's ability to respond to stress. Furthermore, the test measures cortisol four times per day to measure the normality or dysfunction of the diurnal pattern throughout the day.
Urinary Test
The urinary test for cortisol is also known as a 24-hour urinary free cortisol (UFC). Urine is usually collected over 24 hours and then sent to a lab to be analyzed. According to MedlinePlus, a 24-hour urine sample should be collected over two days. The sample should be refrigerated until returned to the lab. Many medications are excreted through the kidneys and may interfere with the testing, so Medline Plus notes that urine cortisol is often tested on at least three different occasions to get a correct reading. The urinary test measures the free, active and unbound portion of the cortisol. The unbound cortisol, according to some theories, correlates better than the bound cortisol to disease symptoms. However, the Journal of Science and Medicine in Sport 2002 article by J.P. Neary concluded that all three testing techniques correlate very well to one another, but that salivary may offer more advantages due to its less cumbersome and non-invasive nature.
