The Prevalence and Death Risk Factors of Nonthyroidal Illness Syndrome in Patients During Hospitalization With Diabetic Foot Ulcers

Background Thyroid hormone abnormalities are common in critical illness and are associated with poor prognosis. The purpose of this study is to investigate the prevalence of nonthyroidal illness syndrome (NTIS) and evaluate its clinical outcomes in hospitalized patients with diabetic foot ulcers (DFUs). Methods A retrospective cohort study was conducted among 997 inpatients with DFU. Patients were stratified into NTIS and non‐NTIS groups based on thyroid function status. Clinical characteristics were compared for each group and for the overall cohort. In addition, the patients were followed up through outpatient interviews or by telephone follow‐up to determine the outcomes, and risk factors for mortality were analyzed. Results Among 727 enrolled DFU patients, 228 (31.4%) were diagnosed with NTIS. Compared with the non‐NTIS group ( n = 499), patients with NTIS exhibited significantly higher levels of fasting blood glucose, glycated hemoglobin, serum creatinine, white blood cells, and C‐reactive protein (CRP), while hemoglobin, albumin, uric acid, and estimated glomerular filtration rate (eGFR) were lower. CRP demonstrated potential utility in predicting foot ulcer healing in DFU patients. Additionally, the prevalence of retinopathy was higher in the NTIS group. During a median 39.0 (IQR 17.4–59.9) months follow‐up period, 215 (29.6%) deaths occurred. Multivariate Cox analysis identified age, free triiodothyronine, peripheral arterial disease, and eGFR as independent risk factors for all‐cause mortality in DFU patients. Conclusion DFU patients with NTIS presented with more severe clinical and metabolic disturbances on admission and experienced worse foot ulcer healing during hospitalization. However, whether the DFU patients were complicated with NTIS or not, there was no significant difference in all‐cause mortality.