RESUMO
OBJECTIVE: To describe euthyroid sick syndrome (ESS) and its different clinical variants in severe acute illness. DESIGN: This prospective cohort study examined hormone results and outcome for patients admitted to our intensive care unit (ICU). METHODS: In this heterogeneous group of 108 patients from our ICU we analyzed the prevalence of ESS and its influence on mortality and sought to determine if any thyroid indicators had a prognostic value. RESULTS: The prevalence of ESS was similar to that described by other authors (68.5% for ESS type I, 15.7% for type II and 1.9% for type III). Patients developed thyroid alterations on their third day of hospitalization and those with ESS type II had a higher mortality rate. The only thyroid indicator with prognostic value was a reverse triiodothyronine (rT3) value exceeding 0.61 ng/mL. CONCLUSION: Severe acute illness induced the thyroid alterations known as ESS. Type I had the highest prevalence, but type II was correlated with a higher mortality rate. The only thyroid indicator with a prognostic value was rT3.