Hair Sample Might Aid in Cushing's Syndrome Diagnosis

Miriam E Tucker

February 13, 2017

Analysis of a hair sample may help in the diagnosis of Cushing's syndrome, a small study suggests.

"Much like hemoglobin A1c is a longitudinal marker of blood glucose levels, hair cortisol can be a measure of the body's glucocorticoid levels over the previous several weeks to months," write Aaron Hodes, MD, of the National Institute of Child Health and Human Development, Bethesda, MD, and colleagues.

Their findings were published online February 13 in Endocrine: International Journal of Basic and Clinical Endocrinology .

In the study of 30 patients with Cushing's syndrome and six controls, cortisol measured in the most proximal (closest to the scalp) 1-cm hair sample was found to be the best marker for reflecting hypercortisolemia compared with more distal samples. Thus, it might serve as an initial or supportive diagnostic test for Cushing's syndrome, for which a diagnosis is challenging and often inconclusive despite numerous tests.

The Endocrine Society Clinical Practice Guideline for diagnosing Cushing's syndrome recommends either a 24-hour urine free cortisol (UFC), 1-mg overnight or 2-mg 48-hour dexamethasone-suppression test, late-night salivary cortisol, or a combination of those tests. However, cortisol levels may fluctuate, and the choice of diagnostic cutoff values can affect test sensitivity and specificity, the group writes, noting that multiple samples are often required for reliability.

Of their 36 patients referred for evaluation of Cushing's syndrome, 30 ultimately received the diagnosis. Cushing's disease was identified as the cause in 20. Hair samples of 3 cm were taken near the scalp, cut into 1-cm proximal, medial, and distal segments, and analyzed for cortisol by enzyme immunoassay performed within 2 months of laboratory testing.

The patients with Cushing's syndrome had significantly higher late-night serum cortisol (435.9 vs 33.1 nmol/L, P < .001) and early-morning cortisol (469.0 vs 259.3 nmol/L, P = .02) than did the controls. They also had significantly greater 24-hour urinary free cortisol corrected for body surface area (UFC/BSA), and 24-hour urinary 17-hydroxysteroids corrected for creatinine (17OHS/Cr), compared with the controls (all < .001).

Proximal-hair cortisol values were higher in the Cushing's syndrome patients than the controls (266.5 vs 38.9 pmol/g, P = .003), while the differences in hair-cortisol values in the medial, distal, and average segments between the Cushing's and control groups did not reach significance.

The proximal 1-cm hair had the highest median cortisol levels of all segments in all patients and controls and represented the highest hair-cortisol level in 69.4% (25/36) of all patients and 73.3% (22/30) of the Cushing's syndrome patients.

In the full study group, there were significant positive correlations between proximal hair cortisol and UFC/BSA (P = 0.005) and midnight serum cortisol (P = .03), while the positive relationship with 17OH/Cr trended toward significance (P = .06).

Among all the Cushing's syndrome patients, there was a positive correlation between proximal hair cortisol and UFC/BSA (P = .009) and early-morning serum cortisol (P = .03) and a trend for midnight serum cortisol (P = .07).

Those relationships were milder for the medial hair segment and were entirely absent in the distal segment. Nor were there significant correlations seen in the subgroup with Cushing's disease.

"Our findings support further investigation into the use of the most proximal 1-cm of hair and hair cortisol in general as an initial or supportive diagnostic test for Cushing's syndrome," Dr Hodes and colleagues conclude.

The authors have no relevant financial relationships.

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Endocrine: Int J Basic Clin Endocrinol. Published online February 13, 2017. Abstract

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