Question: My daughter has just been diagnosed with cyclic cushing’s… I have done some reading and found this article. Is hair testing done in the US?
Answer 1: I’m not aware of any commercial laboratory that offers hair cortisol testing in the U.S. However, it is not clear why this is needed if someone has made the diagnosis and it is clear-cut. There are some things to keep in mind, however, even if the diagnosis is clear. Our testing for the cause of Cushing’s syndrome presumes that cortisol levels are high enough for sufficient time to cause the normal pituitary cells to stop secreting ACTH, the hormone that stimulates the adrenal glands to make cortisol. We call this a feedback system that helps to keep cortisol in the correct range. In patients with cyclic Cushing’s syndrome, it is possible that the cortisol levels are not high enough or don’t stay high long enough to stop ACTH from the normal cells. In that case, when we measure ACTH to help determine the cause of Cushing’s, it is possible that we will measure ACTH from the normal cells and get a misleading result. For this reason, my group asks patients, especially those with possible cyclic Cushing’s syndrome, to measure a 24-hour urine for cortisol, and obtain a salivary cortisol at bedtime on that day. We do this once a week for six weeks, and if the numbers are high, we admit to evaluate for the cause of Cushing’s syndrome. (Dr. Lynnette Nieman, NIH)
Answer 2: I’m not aware of a lab in the US performing this for patient care. It is an interesting concept that is worth researching more and might be a useful diagnostic tool for the future. The patients included in this study have fairly high 24h urine cortisol levels and it would be interesting to see more patients with milder Cushing and pseudo-Cushing (endogenous elevated cortisol not related to a tumor) to tease out a cutoff/normal range that would be helpful in early diagnosis. (Dr. Georgiana Dobri, Cornell)
Answer 3: Hair cortisol is not available for routine use in the clinic at present. However, it is being used in research studies in several countries. Although it appears promising, its value as a test in patients with suspected (cyclic) Cushing’s remains to be proven. It is not clear, for example, if hair dyes, shampoos and exposure to the elements (sun, water) can affect hair cortisol levels. More research is needed before this test can be recommended to our patients. (Dr. Nicholas Tritos, Massachusetts General Hospital)