Problems Interpreting Cortisol Lab Tests in Adrenal Fatigue
Posted by Dr. James Wilson on Thu, Oct 08, 2009
Complicating the problem of proper interpretation of laboratory data in adrenal fatigue is the fact that steroid hormones occur in more than one form in your body, but most lab tests measure only one.
Cortisol, for example, takes on three forms in your blood: 1) unattached to any other substance (free), 2) loosely bound and, 3) tightly bound to blood proteins. The most common measurement for hormones is the amount of hormone not attached to anything, called the free circulating hormone. However, this usually represents a meager 1% of the total amount of hormone available. It does not measure the bound hormones, which act as reserves and become free hormones if needed. This reserve can be critical to proper physiological function. For example, very low circulating cortisol levels can be brought to within normal range by the administration of a synthetic cortisol. But people taking synthetic cortisol cannot withstand stress as well as people with naturally normal cortisol levels, even though blood tests for both show normal free circulating cortisol levels. One reason for this is that although free circulating cortisol levels are increased by taking the synthetic cortisol, levels remain low of tissue bound cortisol that provides reserve stores in cases of emergency (stress). Blood tests can often be deceptive because they do not typically give you the whole picture. Therefore, even though both healthy people and people taking cortisol might show normal free cortisol levels, their response to stress will probably differ considerably. The test results would give a very deceptive picture of "normal" in the case of the person receiving the drug, as it tests only the most superficial layer of cortisol availability.
In adrenal function, the extreme low on a bell curve is Addison's disease and the extreme high is Cushing's disease. The other 95% represents an enormous variation in levels of adrenal function that is usually disregarded by lab computers and overlooked by doctors because the scores in this range do not fall into either of the two extreme or "diseased" categories. By default, any scores falling within this range (95%) are considered "normal" The end result of basing laboratory test scores on statistics rather than on signs and symptoms is that many people who have mild to moderately severe adrenal fatigue are never accurately diagnosed; they look "normal" on the tests.
Stress is a factor that significantly affects adrenal hormone levels. Your cortisol level tested after a quiet, relaxing morning will be very different from your cortisol level tested when you are under stress before you arrive at the lab. To obtain a typical value, have your test on a typical morning.