Prevalence and prognostic value of non-thyroidal illness syndrome among critically ill children

Abstract

IntroductionAlterations in thyroid hormones during critical illness, known as non-thyroidal illness syndrome (NTIS), were suggested to have a prognostic value. However, paediatric data is limited. The aim of this study was to assess prevalence and prognostic value of NTIS among critically ill children. Materials and methodsA prospective observational study conducted on 70 critically ill children admitted into paediatric intensive care unit (PICU). Free triiodothyronine (FT3), free thyroxine (FT4), and thyroid stimulating hormone (TSH) were measured within 24h of PICU admission. Primary outcome was 30-day mortality. ResultsNTIS occurred in 62.9% of patients but it took several forms. The commonest pattern was low FT3 with normal FT4 and TSH (25.7% of patients). Combined decrease in FT3, FT4, and TSH levels occurred in 7.1% of patients. An unusual finding of elevated TSH was noted in three patients, which might be related to disease severity. Low FT4 was significantly more prevalent among non-survivors compared with survivors (50% versus 19.2%, P=.028). NTIS independently predicted mortality (OR=3.91; 95% CI=1.006–15.19; P=.0491). Concomitant decrease in FT3, FT4, and TSH was the best independent predictor of mortality (OR=16.9; 95% CI=1.40–203.04; P=.026). TSH was negatively correlated with length of PICU stay (rs=—0.35, P=.011). FT3 level was significantly lower among patients who received dopamine infusion compared with those who did not receive it (2.1±0.66 versus 2.76±0.91pg/mL, P=.011). ConclusionNTIS is common among critically ill children and appears to be associated with mortality and illness severity.