Context and objectives: To elucidate the influence of disease severity, deiodination, sulfation, thyroid hormone binding and dopamine use on thyroid function in euthyroid sick syndrome.

Setting: University-affiliated pediatric intensive care unit (PICU).

Design: Observational cohort study.

Patients: Sixty-nine children with meningococcal sepsis.

Main outcome measures: Differences in thyroid function between nonsurvivors, shock-survivors and sepsis-survivors on PICU admission.

Results: The main study group consisted of 45 non-dopamine-treated children. All children had decreased TT3/rT3ratios without elevated TSH. T4-sulfate levels were decreased in 88%. Nonsurvivors had paradoxically higher TT3/rT3ratios than shock-survivors (0.71 vs. 0.30), this ratio also correlated with shorter duration of disease (r = -0.43). TT4 and TBG levels declined with increasing disease severity. TBG levels correlated inversely with elastase levels (r = -0.46). Only TSH levels were significantly lower in 24 dopamine-treated children compared with non-dopamine-treated children (0.65 vs. 0.84), whereas other thyroid hormones did not significantly differ. Both higher TT3/rT3ratios and lower TT4 levels were predictive for mortality, but this disappeared when IL-6 was entered in the regression model.

Conclusions: All children with meningococcal sepsis showed signs of euthyroid sick syndrome. Alterations in peripheral thyroid hormone metabolism related inversely with duration of disease and seemed enacted by profound induction of type 3 deiodinase rather than down-regulation of type 1. Lower TT4 levels were related to increased turnover of TBG by elastase. Dopamine was found to only suppress TSH secretion, but not other thyroid hormone levels on PICU admission. Both TT3/rT3 ratio and TT4 levels were predictive for mortality, but not superior to IL-6.