Nonthyroidal Illness Syndrome and Hypothyroidism in Ischemic Heart Disease Population: A Systematic Review and Meta-Analysis

Context: The association of non-thyroidal illness syndrome (NTIS) and hypothyroidism with the prognosis in ischemic heart disease (IHD) population is inconclusive. Objective: We aimed to evaluate the influence of NTIS and hypothyroidism on all-cause mortality and major adverse cardiac events (MACE) in IHD population. Data Sources: We searched PubMed, EMBASE, Scopus, Web of Science, and Cochrane Library from inception through February 17, 2020. Study Selection: Original articles enrolling IHD patients, comparing all-cause mortality and MACE of NTIS and hypothyroidism with those of euthyroidism, and providing sufficient information for meta-analysis were considered eligible. Data Extraction: Relevant information and numerical data were extracted for methodological assessment and meta-analysis. Data Synthesis: Twenty-three studies were included. The IHD population with NTIS was associated with higher risk of all-cause mortality (hazard ratio [HR] = 2.61; 95% confidence interval [CI] = 1.89-3.59) and MACE (HR = 2.22; 95% CI = 1.71-2.89) than that without. In addition, the IHD population with hypothyroidism was also associated with higher risk of all-cause mortality (HR = 1.47; 95% CI = 1.10-1.97) and MACE (HR = 1.53; 95% CI = 1.19-1.97) than that without. In the subgroup analysis, the acute coronary syndrome (ACS) subpopulation with NTIS was associated with higher risk of all-cause mortality (HR = 3.30; 95% CI = 2.43-4.48) and MACE (HR = 2.19; 95% CI = 1.45-3.30). The ACS subpopulation with hypothyroidism was also associated with higher risk of all-cause mortality (HR = 1.67; 95% CI = 1.17-2.39). Conclusions: The IHD population with concomitant NTIS or hypothyroidism was associated with higher risk of all-cause mortality and MACE. Future research is required to provide evidence of the causal relationship and to elucidate whether normalizing thyroid function parameters can improve prognosis.