Thyroid Function, Reverse Triiodothyronine, and Mortality in Critically Ill Clinical Patients.

Area of Science:

• Endocrinology
• Critical Care Medicine
• Clinical Biochemistry

Background:

• Critically ill patients often exhibit thyroid hormone alterations.
• The association between elevated reverse triiodothyronine (rT3) and mortality in this population requires further investigation.

Purpose of the Study:

• To determine the relationship between changes in thyroid hormones, specifically increased rT3, and mortality in critically ill clinical patients.
• To assess the predictive value of rT3 levels for intensive care unit (ICU) mortality.

Main Methods:

• Prospective observational study of 353 consecutive adult ICU patients in Brazil.
• Measurement of thyroid hormones (T4, fT4, T3, fT3, rT3, TSH) within 48 hours of admission.
• Exclusion of patients with pre-existing hypothyroidism or hyperthyroidism.

Main Results:

• ICU mortality was 17.6%. Non-survivors had higher rT3 levels (69.3% vs 59.2%, p=0.042) and increased age, SOFA, and APACHE II scores.
• Increased rT3 (OR: 2.436; 95% CI: 1.023-5.800; p=0.020) and APACHE II score were independently associated with ICU mortality in multivariate analysis.
• No significant association was found between other thyroid hormone alterations and mortality.

Conclusions:

• Elevated rT3 levels are an independent predictor of increased ICU mortality in critically ill clinical patients.
• rT3 measurement can be a valuable tool for risk stratification in the ICU.
• Thyroid hormone changes, apart from rT3, did not demonstrate a significant association with mortality in this cohort.