Relationship between disease severity and thyroid function in Chinese patients with euthyroid sick syndrome

Euthyroid sick syndrome (ESS) is commonly observed in various acute and chronic illness as risk factor for mortality in patients with severe diseases, with lower triiodothyronine (T3) and free triiodothyronine (fT3). To explore the relationship between disease severity and thyroid function in critically ill Chinese patients with ESS. A total of 51 patients admitted to intensive care unit were examined to determine acute physiology and chronic health assessment II (APACHE II) scores within 24 hours of admission; thyroid function tests (TSH, fT3, fT4, tT3, tT4) and rT3 levels were determined on the second day. Based on the test results, patients were divided into euthyroid (n = 13), decreased fT3 or fT4 (n = 17), and decreased TSH (n = 21) groups. APACHE II scores and thyroid function were compared between the 3 groups. Furthermore, the relationship between the severity of disease and euthyroid sick syndrome was assessed. Out of 51 patients, 38 were men and 13 were women [mean age (± SD): 60.39 (± 19.32) years; range, 15–88 years]. APACHE II scores and rT3 levels were increased in all the 3 groups (P > .05). APACHE II scores showed a positive correlation with rT3 (P = .004, r = 0.379). Critically ill Chinese patients with ESS have a poor health state. Higher rT3 values are associated with severe disease.