Aim of the study was to investigate the status of thyroid homeostasis and the relationship between severe traumatic brain injury (TBI) and thyroid disorders. The study included 56 patients. Protocol of the study concluded: noninvasive and invasive hemodynamic monitoring, including PICCO, transcranial Doppler ultrasonography, measurement of intracranial pressure (ICP), indirect calorimetry, levels of thyroid stimulating hormone (TSH), T3, T4 and free fractions. Patients were divided into three groups. Group 1--with normal thyroid hormones (n = 20), Group 2--with the low T3 (n = 23) and Group 3 with the low T3 and T4 (n = 13). Correlation between the Glasgow Coma Scale (GCS) and thyroid hormone levels was obtained: the first group between GCS and T4 (r = 0.50), GCS, and free fraction T4 (r = 0.51); between the GCS and TSH (r = 0.51), T3 (r = 0.48) and T4 (r = 0.57) in the second group, and the third--with TSH (r = 0.67). Poor outcomes in the first group compound 15%, in the second group--39.2%, and in the third group--62.5% of patients. Doses of vasopressors were significantly higher in groups 2 and 3 compared with a first group. ICP was significantly higher in the group with the low T3 and T4. Development of intracranial hypertension correlated with the formation of thyroid insufficiency. Deficiency of thyroid hormones, especially the simultaneous reduction and T3, and T4 is associated with poor outcome in patients with severe TBI. Doses of sympathomimetic drugs used to optimize the parameters of systemic hemodynamics in acute severe head injury were higher in patients with deficiency of thyroid hormones.