Relationship of thyroid function to post-traumatic S-100b serum levels in survivors of severe head injury: preliminary results

Abstract

Objective: To assess thyroid function abnormalities in survivors of severe head trauma and to examine their relationship with indices of brain injury severity.

Design: Prospective study.

Setting: General intensive care unit (ICU) in a university hospital.

Patients and participants: Twenty-two (21 men) head-injured patients, with a median age of 25.5 years at the time of injury, were investigated. Severity of brain trauma was assessed by Glasgow Coma Scale (GCS) score, Marshall Computerized Tomographic Classification, intracranial pressure levels and serum S-100b concentrations measured over a 6-day period.

Interventions: Thyroid function testing was performed 1 year after ICU discharge and included the measurement of free thyroxine, triiodothyronine and thyrotropin.

Measurements and results: On admission to the ICU, GCS ranged from 3 to 8. Peak S-100b was 1.49 microg/l (range: 0.37-5.26 microg/l). Median triiodothyronine and thyrotropin were 123 ng/dl and 1.60 microIU/ml, respectively. Free thyroxine was 1.08+/-0.22 ng/dl (range: 0.7-1.5 ng/dl). Overall, 7 of the 22 patients (32%) had thyroid dysfunction. Four patients had central hypothyroidism and three patients had subclinical hypothyroidism. Peak S-100b correlated negatively with free thyroxine (r=-0.47, p=0.02). There were no correlations between other brain injury severity indices and thyroid hormone levels.

Conclusions: A significant subset of brain injury patients presents with changes in thyroid function 1 year after ICU discharge; these depend upon biochemical serum markers of head trauma severity.