Does Having a High Morning Cortisol Mean I Have Cushing’s Disease?
The answer is no for 2 reasons. First of all, I did a study when I was at the NIH about 25 years ago showing that people with Cushing’s syndrome and those tested for Cushing’s syndrome and not having it, have similar morning cortisol [Friedman, T.C. and Yanovski, J.A. (1995) Morning Plasma Free Cortisol: Inability to Distinguish Patients with Mild Cushing Syndrome from Patients with Pseudo-Cushing States. J. Endocrinol. Invest. 18:696-701. PMID: 8719300]. It is the nighttime cortisol that is important to test in Cushing syndrome, as people with Cushing syndrome have high nighttime cortisol while normal individuals have low nighttime cortisol.
Also, patients taking oral estrogens or birth control pills will have a high morning cortisol, but it does not mean they have Cushing’s. That is because oral estrogen and birth control pills raise the cortisol-binding globulin (CBG) which leads to high total cortisol, as it is bound to the cortisol- binding globulin. However, the free cortisol which the cortisol receptors in the body sees, is normal. Many patients come to see me with a high morning cortisol due to being on birth control pills, and I have to explain to them that it does not mean they have Cushing’s syndrome.
If you would like more information, please do not hesitate to make an appointment or visit Dr. Friedman’s website at goodhormonehealth.com.