I started this blog post during last year's Cushing's Awareness Blogger's Challenge in April, and never finished it because it felt like a Herculean task. I do believe it is important information and it turns out I had the energy to delve into it some today, but I'm going to split it into separate posts because there is a fair amount of information to cover and I only have so much energy and brainpower each day. Below is the intro and I'll make a separate post on each different type of test in the upcoming days.
There are various tests used to look for high cortisol levels within the body. None is perfect and each has it's inherent strengths and weaknesses. Not all test types will work for everyone, and they won't show a diagnostic high every time you test either, unless you have a more florid form of the disease (ie, always high all the time). Most of us are diagnosed off of a mixture of these tests, and they often have to be repeated many times. Here are the most common:
24 hour Urinary Free Cortisol (UFC)
24 hour 17-hydroxycorticosteroids (17 ohc/17ohs)
10 hour Urinary Free Cortisol
Midnight Serum Cortisol
Serum Adrenal Corticotropin Releasing Hormone (ACTH)
Serum Cortisol Binding Globulin (CBG)
Dexamethasone Suppression Tests (Dex)
Inferior Petrosal Sinus Sampling (IPSS)
Imaging such as MRI's and CT's
For most patients, we have to do a series of tests, usually in about 3
different types, before we get our official diagnosis and move on to treatment. My endocrinologist typically runs 3 or 4 each of 3
different types of tests when suspicion is high for Cushing's (saliva,
24 hr UFC, and either he tags on 17ohc's to each of those 24hr samples or he might
order 10 hour UFC's if he suspects you are more cyclic with higher
cortisol at night and lower cortisol in the day --it just all depends on your specific case) , along with a midnight
serum cortisol and ACTH level after your appointment while in his office,
testing of other hormones, and usually he orders an 8am lab to be done
when you get home as well (8am serum cortisol, ACTH, and maybe other
hormones, vitamin D, and often ferritin as well).
I personally did countless 24hr UFC's, 17ohc's, 10 hr UFC's, Midnight Serums, a handful of ACTH's (midnight and 8am), and a handful of midnight salivary cortisols. I got many diagnostic highs in every test type *except* for salivary. (Sad, too, cause they are the easiest to do!) We don't know why, but patient experience seems to show that it is QUITE common for a patient to test high in some tests and not in others...which tests work best varies from patient to patient and from case to case.
(If I miss something important, please feel free to contact me and I'll update as necessary.)