Study of Non-Thyroidal Illness Syndrome and Its Recovery in Critically Ill Patients at a Tertiary Care Centre in South India.

BACKGROUND AND OBJECTIVES

Transient thyroid hormone alterations are common during critical illness and are termed non-thyroidal illness syndrome (NTIS). We studied the prevalence of NTIS in the ICU setting and its impact on predicting mortality and other outcomes and compared it to the Acute Physiology and Chronic Health Evaluation II (APACHE II) score.

MATERIALS AND METHODS

The study included 119 consecutive patients admitted with a critical illness. APACHE II score was calculated. Total T3, total T4, TSH, free T3, and free T4 were measured at admission and after six weeks of discharge. NTIS and euthyroid groups were studied for ICU, hospital stays, mortality, readmission, and recovery. Predictors of mortality were compared between survivors and non-survivors.

RESULTS

The mean age was 60.15 ± 14.50 years with M:F = 84 (71%):35 (29%). NTIS was observed in 84 (71%), low T3 being the most common abnormality in 53 (63%). The occurrence of NTIS was significantly higher among non-survivors (28/30, 93%) versus survivors (56/89, 63%) ( = 0.002). Non-survivors showed significantly lower T3, TSH, and FT3/FT4 ratios and higher readmissions. NTIS group showed significantly greater ICU stay ( = 0.02) and had higher readmission rates ( = 0.032). Baseline T3 had the greatest power to predict mortality. APACHE II score also correlated significantly with mortality (19.60 ± 10.58 vs 11.99 ± 6.80, < 0.001). The area under the curve (0.677) for the T3 level was lower than the APACHE II score (0.760). After six weeks, 61% had recovered from NTIS.

CONCLUSIONS

NTIS was common amongst critically ill patients (71.5%), which reversed in 61% at six weeks. Low T3 was the most common abnormality and independently predicted mortality. Free T3/free T4 also significantly predicted mortality. The correlation between thyroid dysfunction and the severity of primary illness makes it an additional attractive low-cost marker of mortality.