Non-thyroidal illness syndrome in cardiology: insights into pathogenesis, diagnosis, and treatment approaches

Euthyroid sick syndrome (ESS), also known as non-thyroidal illness syndrome (NTIS), is characterized by abnormal thyroid function test results in patients without intrinsic thyroid disease, often observed in critically diseased patients. This review evaluates the current understanding of ESS in daily cardiology practice, including its pathogenesis, diagnostic criteria, and therapeutic approaches, with a focus on ICU patients. Recent advances in research on the role of inflammatory cytokines and the impact of thyroid hormone replacement therapy are also discussed. A total of 1,346 records were found (432 in MEDLINE, 586 in Web of Science, and 328 in Scopus), and 142 duplicates were removed. All titles with an abstract were reviewed, and 89 qualified for a full review of eligibility. Eight articles met the inclusion criteria and were qualitatively summarized in this review. with a PRISMA flowchart illustrating the selection process. This systematic review underscores the importance of recognizing ESS in cardiology practice, as its management may impact cardiovascular outcomes.