Determination of thyroid hormones in human hair with online SPE LC-MS/MS: Analytical protocol and application in study of burnout.

Thyroid hormones (THs) play a key role within the endocrine system. Incorporated biomarkers in hair can reflect endogenous excretion patterns over several months. We present an online solid phase extraction-liquid chromatography-mass spectrometry (online SPE-LC-MS/MS) method for quantification of THs in human hair and test it in the volunteers suffering from different severity of burnout symptom. THs were extracted from 7.5 mg hair by methanol incubation. Extracts were analyzed with LC-MS/MS in positive electrospray ionization mode. Burnout symptoms were assessed with the Maslach Burnout Inventory-General Survey (MBI-GS). THs levels were determined in 208 hair samples from adults and related to individual MBI-GS score. Intra- and inter-day coefficients of variance were between 3.1% and 10.2%. The recoveries of this method were between 88.5% and 102.1%. Hair T4 levels correlated significantly with total and free T4 in plasma. Participants with high degree of burnout had significantly higher hair T4 levels and lower T3/T4 ratio compared to those with no or moderate degree of burnout. A trend towards higher hair T3 levels was observed in subjects with high burnout score. Hair T4 levels showed a significant positive relationship with MBI-GS score, whereas no significant correlation emerged for hair T3 levels. The negative correlation between T3/T4 ratio and MBI-GS score was also significant. We have developed an online SPE-LC-MS/MS method for measurement of THs in human hair, allowing high analytical specificity and sensitivity. The novel finding of hair THs levels from individuals suffering from chronic stress in burnout underscores the relevance of this method for medical and psychological research.