Currently available methods for endogenous cortisol monitoring in patients with hormonal insufficiency rely on measurements of plasma levels only at a single time point; thus, any kind of chronic exposure to cortisol is challenging to evaluate because it requires collecting samples at different time points. Hair cortisol levels acquired longitudinally better reflected chronic exposure (both cortisol synthesis and deposition) and may significantly contribute to better outcomes in glucocorticoid replacement therapies.
Twenty-two patients on cortisol substitution therapy were monitored for plasma, urinary, and hair cortisol levels for 18 months to determine whether hair cortisol may serve as a monitoring option for therapy setting and adjustment.
Plasma and urinary cortisol levels were measured using standardized immunoassay methods, and segmented (∼1 cm) hair cortisol levels were monitored by liquid chromatography coupled to mass spectrometry. A log-normal model of the changes over time was proposed, and Bayesian statistics were used to compare plasma, urinary, and hair cortisol levels over 18 months.
Results and conclusions:
Hair cortisol levels decreased over time in patients undergoing substitutional therapy. The residual variance of hair cortisol in comparison to plasma or urinary cortisol levels was much lower. Thus, longitudinal monitoring of hair cortisol levels could prove beneficial as a noninvasive tool to reduce the risk of overdosing and improve the overall patient health.