Thyroid hormones as potential prognostic factors in sepsis

Background
Sepsis is a life-threatening organ dysfunction caused by a dysregulated host reaction to infection. There is an upward trend in sepsis prevalence and mortality worldwide. Sepsis causes hypoxia, which reduces the ability of cells to produce ATP. This process is also influenced by thyroid hormones. Some of the previous studies revealed association between the mortality rate in sepsis and thyroid hormone levels. We aimed to evaluate thyroid hormones’ predictive value in septic patients.

Methods
Forty-nine adult patients with sepsis admitted to the Intensive Care Unit of Allergy and Immunology Department at the University Hospital in Krakow, Poland, between 2015 and 2017 were enrolled in the study. Blood samples were obtained from septic patients immediately after establishing the diagnosis, in order to measure free triiodothyronine (fT3), free thyroxine (fT4), and thyroid-stimulating hormone (TSH) levels. The primary endpoint was 30-day survival rate. The secondary endpoint was death anytime during intensive care unit (ICU) stay.

Results
Patients who died within 30 days had significantly lower level of fT4 than survivors (9.8 vs. 12.7 pmol L^-1; P = 0.033). There was no statistically significant difference between the groups in TSH and fT3 levels. As for the secondary endpoint, both fT3 (1.6 vs. 1.8 pmol L^-1; P = 0.021) and fT4 (9.8 vs. 12.7 µIU mL^-1; P = 0.019) levels were significantly lower among non-survivors compared to survivors, which was not the case for TSH.

Conclusions
Thyroid hormone levels were significantly lower among patients who died during ICU stay. The results of the presented study suggest that fT3 and fT4 levels may be taken into consideration as potential new prognostic factors in sepsis.