Hair cortisol in the evaluation of Cushing syndrome

Hair cortisol evaluation has been used to help detect patients with suspected Cushing syndrome. Our goal was to correlate segmental hair cortisol with biochemical testing in patients with Cushing syndrome and controls. This study was a prospective analysis of hair cortisol in confirmed Cushing syndrome cases over 16 months.

Thirty-six subjects (26.5 ± 18.9 years, 75% female, and 75% Caucasian) were analyzed by diurnal serum cortisol, 24 h urinary free cortisol corrected for body surface area (UFC/BSA), and 24 h urinary 17-hydroxysteroids corrected for creatinine (17OHS/Cr). Thirty patients were diagnosed with Cushing syndrome, and six were defined as controls. 3-cm hair samples nearest to the scalp, cut into 1-cm segments (proximal, medial, and distal), were analyzed for cortisol by enzyme immunoassay and measured as pmol cortisol/g dry hair. Hair cortisol levels were compared with laboratory testing done within previous 2 months of the evaluation.

Proximal hair cortisol was higher in Cushing syndrome patients (266.6 ± 738.4 pmol/g) than control patients (38.9 ± 25.3 pmol/g) (p = 0.003). Proximal hair cortisol was highest of all segments in 25/36 (69%) patients. Among all subjects, proximal hair cortisol was strongly correlated with UFC/BSA (r = 0.5, p = 0.005), midnight serum cortisol (r = 0.4, p = 0.03), and 17OHS/Cr, which trended towards significance (r = 0.3, p = 0.06).

Among the three examined hair segments, proximal hair contained the highest cortisol levels and correlated the most with the initial biochemical tests for Cushing syndrome in our study. Further studies are needed to validate proximal hair cortisol in the diagnostic workup for Cushing syndrome.