Patients with mutations of the Thyroid hormone beta-receptor show an ADHD-like phenotype for performance monitoring: an electrophysiological study

Resistance to thyroid hormone beta (RTH beta) is a syndrome of reduced responsiveness of peripheral tissue to thyroid hormone, caused by mutations in the thyroid hormone receptor beta (THRB). Its cognitive phenotype has been reported to be similar to attention deficit hyperactivity disorder (ADHD). This study used electrophysiological biomarkers of performance monitoring in RTH beta to contribute further evidence on its phenotypical similarity to ADHD. Twenty-one participants with RTH beta aged 18-67 years and 21 matched healthy controls performed a modified flanker task during EEG recording. The RTH beta and control groups were compared on behavioural measures and components of event related potentials (ERPs), i.e. the error related negativity (ERN), the error positivity (Pe) and P3 component. There were no significant group differences with regard to behaviour. RTH beta subjects displayed significantly reduced ERN and Pe amplitudes compared to the controls in the response-locked ERPs. In addition, we observed reduced P3 amplitudes in both congruent and incongruent trials, as well as prolonged P3 latencies in RTH beta subjects in the stimulus-locked ERPs. Our findings reveal alterations in error detection and performance monitoring of RTH beta patients, likely indicating reduced error awareness. The electrophysiological phenotype of RTH beta subjects with regard to action monitoring is indistinguishable from ADHD.