Thyroid and thymic endocrine function and survival in severely traumatized patients with or without head injury

Objective: Functional links among the brain, endocrine and immune system have been described previously. An impairment of both immunological defence mechanisms and thyroid hormone turnover was present in trauma conditions. An investigation on the relevance of thymulin and thyroid hormones in multiple trauma patients with or without head injury has been performed. The role of these hormones as predictive factors for patients outcome was also evaluated. Design: Plasma thymulin levels and plasma thyroid hormone concentrations were tested in multiple trauma patients 24 h after admission to the Intensive Care Unit (ICU) and again after 5 and 10 days. Setting: Department of Immunology Ctr. INRCA, IInd ICU, S. Matteo Hospital Pavia and ICU "Umberto I" Hospital, Ancona. Patients: 45 patients were evaluated including 14 multiple trauma patients without head injury and 31 multiple trauma patients with head injury at various level of coma, graded according to the Glascow Coma Score (GCS). Interventions: Routine protocol interventions were performed in all head injured patients. Measurements and results: Thymulin and triiodothyronine (T₃) levels were reduced, and reverse triiodothyronine (fT3) increased in all traumatized patients, but multiple trauma patients with head injury and GCS≤5 had the lowest levels of thymulin and T₃ and the highest levels of rT₃. No difference in plasma thyroxine (T₄) and thyrotropin (TSH) levels was observed among injured patients. The analysis of predictive factors for the outcome has assigned to thymulin the highest score (29.6%) compared with the score for T₃ (19.3%) and rT₃ (26.3%). The total relative risk (Δ%) calculated on the basis of T₃ or rT₃ rises significantly when thymulin relative risk is added. Conclutions: Thymulin is markedly reduced in multiple trauma patients with head injury and it represents a predictive factor for the outcome better than the one deriving from the single measurements restricted to thyroid hormones.