Triiodothyronine replacement in critically ill adults with non-thyroidal illness syndrome

Non-thyroidal illness syndrome is commonly encountered in critically ill patients, many of whom are treated with thyroid hormones despite uncertainty regarding their safety and effectiveness. This retrospective observational study sought to evaluate the utilization, safety, and effectiveness of triiodothyronine (T3) supplementation in critically ill adults admitted to either of two non-cardiac surgery mixed-medical/surgical intensive care units (ICU).

Consecutive adults admitted to an ICU and treated with enterally administered T3 were identified over a two-year period. Data pertaining to demographics, T3 utilization, safety, and clinical outcomes were collected.

Data were extracted from the medical records of 70 consecutive patients. All had baseline serum free T3 concentrations below the lower limit of our laboratory's reference range and 22 (31%) patients also had low thyroxine (T4) concentrations. The most commonly prescribed replacement doses were 25 and 50 µg for a median of seven days and almost half of the patients also received concomitant T4 supplementation. Serum thyroid hormones were available in 48 of 70 patients (69%) at a median [interquartile range (IQR)] of 7 [6-38] days. Normalization of free T3 serum concentrations occurred in 30 of 48 patients (63%) at a median [IQR] of 8 [7-33] days. A dose-response relationship was identifiable. New adverse events (atrial fibrillation/flutter, hypertension, sinus tachycardia, myocardial infarction) during therapy were less frequent than at baseline.

This study suggests that with T3 supplementation there was evidence of serum free T3 normalization without evidence of associated harms. A definitive trial is needed to evaluate clinical effectiveness.