Background Currently, the elderly population is rapidly increasing, and elderly patients with non-thyroidal illness syndrome (NTIS) in intensive care units (ICUs) have relatively severe symptoms and a poor prognosis. However, there are few studies on the correlation between NTIS and patient mortality among hospitalised elderly patients in the general ward.Methods In the present study, 931 male inpatients ≥ 60 years of age who visited our hospital from January 2012 to December 2013 were selected

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... and divided into the NTIS group and normal thyroid function (non-NTIS) group. Propensity score matching was used to match the two groups according to age and body mass index. Thyroid function, serum proteins, metabolic indicators, liver and kidney function and mortality were collected.Results Serum total protein (TP), albumin (Alb), prealbumin (PA), haemoglobin (Hb), uric acid (UA), triglyceride (TG), and high-density lipoprotein cholesterol (HDLC) levels were significantly lower in the NTIS group than in the non-NTIS group. The urea nitrogen (UN) and fasting blood glucose (FBG) levels were higher in the NTIS group than in the non-NTIS group. Total T3, TP, Alb, and PA levels were positively correlated with the Hb level and negatively correlated with FBG, UN, and creatinine (Cr) levels. The free T3 level was positively correlated with TP, Alb, PA, Hb, and UA levels and negatively correlated with FBG, UN, and Cr levels. Multivariate Cox proportional hazards models indicated that a lower free T3 level was associated with increased all-cause mortality after adjusting for covariates. The patients in the NTIS group had a lower survival rate at 2 years based on Kaplan–Meier survival curves. Receiver operating characteristic curve (ROC) analysis showed that a cut-off free T3 level of 3.445 pmol/L yielded the highest sensitivity and specificity for predicting all-cause mortality at 2 years.Conclusion Among elderly male inpatients, the survival rate was lower in the NTIS group than non-NTIS group. Serum protein levels and renal function decreased and the FBG level increased with decreasing total T3 and free T3 levels. A decreased free T3 level in hospitalized elderly male patients was a predictor of poor prognosis.