Observational and Diagnostical Study on Transient Allostatic Responses of Thyroid Function After Syncopation and Seizure

Transient allostatic responses of thyroid function have been described in critical illness. Own observations suggest similar reactive responses after syncopation and cerebral seizures. They are marked especially by increased concentration of serum thyrotropin (TSH), suggesting a type 2 allostatic response. However, changes of thyroid function after temporal loss of consciousness haven't been systematically evaluated up to now. Current diagnostic guidelines recommend primarily the determination of serum TSH concentration for screening of thyroid function, and the measurement of peripheral thyroid hormones (T4 and/or T3) is only recommended if TSH determination results in pathological values. This TSH reflex strategy may be misleading after short-term loss of consciousness. This study aims at assessing the prevalence of allostatic responses of thyroid function after events of syncopation or seizure and at investigating the consecutive temporal development of biomarkers of thyroid function. An additional aim includes the diagnostic value of TSH determination, compared to measurement of free thyroid hormones, for thyroid dysfunction after syncopation or seizure. Results of this study might contribute to an improved detection rate of thyrotoxicosis. In cases of medical emergencies and in-patient treatment interventions with a significant iodine load are common, including the application of iodinated radiocontrast agents and amiodarone. In this setting, undetected hyperthyroidism may lead to thyroid storm, which is associated with a high mortality.