Are Changes in Thyroid Hormones Associated with Mortality in Non-Thyroidal Illness Syndrome?

Abstract

Introduction: Non-thyroidal illness syndrome (NTIS) can be defined as afunctional impairment of the hypothalamic-pituitary-thyroid axis accompanied by signs of non-thyroidal disease with changes in thyroid stimulating hormone (TSH), free T3 (fT3) and free T4 (fT4) levels. NTIS and thyroid hormone levels in this syndrome are thought to be related with mortality. This study was performed to evaluate the relationship between hormone levels and mortality in this syndrome.
 Methods: The 5-year mortality data of patients who were hospitalized in the first 6 months of 2014 and whose thyroid hormone levels could be checked twice within 5 years were evaluated. In our study conducted with 405 patients whose thyroid function tests was repeated, the follow-up period was 5 years. Biochemical parameters including thyroid function tests were sent from all patients. NTIS was defined as a condition in patients with low fT3 levels (<2.5 pg/mL) and TSH levels within the normal range (0.38-5.33 mIU / L).
 Results: 128 patients died, and the number of surviving patients was 277 during the follow-up period. Positive acute phase reactants such as CRP, sedimentation, ferritin was high and albumin (negative acute phase reactant) and fT3 levels were low in patients who died. In addition, these changes in biochemical values were statistically significant. The mortality rate was increased in patients with low fT3 and high fT4 levels. In the follow-up period, changes in TSH levels were not significantly associated with mortality.
 Conclusion: Both the decrease in fT3 levels and the increase in fT4 levels can be used as predictors and independent risk factors for long-term mortality risk in chronically ill and hospitalized patients with NTIS.