Objective To investigate the effects of risk factors on non thyroidal Illness syndrome (NTIS) in elderly inpatients.Methods A total of 819 elderly inpatients who met inclusion criteria were consecutively recruited in thiscross-sectional study.Physicalmeasurements and mini nutritional assessment using the mini nutritional assessment-short form (MNA-SF) score were conducted.A serum levels of thyroid stimulating hormone (TSH),free triiodothyronine (FT3),free thyroxine (FT4),brain natriuretic peptide (BNP) and C-reactive protein (CRP) were examined.Data were analyzed with multivariatelogistic regression.Results The significant differences were found between NTIS group (n=145) versus control group (n=674)inage (78.5±8.1) years vs.(75.1±8.6) years(t=5.422,P＜0.01),in body mass index (23.0 ±3.8) kg/m2 vs.(24.1±3.6) kg/m2,in MNA-SF score 11.2±2.3 vs.12.3± 1.8(t=-3.315,6.754,P＜0.01),in level of serum albumin (36.0±4.5) g/L vs.(38.4±3.6) g/L (t=-6.977,P＜0.01),in triglyceride level (1.3± 0.9) mmol/L vs.(1.5±1.0) mmol/L(t=-3.039,P＜0.01),inCRP (Z=-8.857,P＜0.01)),and in BNP (t=6.331,P＜0.01).Logistic regression analysis revealed that age＞ =80 years (OR=2.433,95％CI:1.357 4.361),malnutrition (OR=1.946,95％CI:1.261-3.001),renal insufficiency (eG FR＜60 ml/min,OR =2.131,95％ CI:1.367-3.322),and high level of CRP (10 mg/L and 50 mg/L:OR=3.446,95％CI:2.117-5.611;over 50 mg/L:OR =10.029,95％CI:4.693-21.432,all P＜0.01)) were risk factors for NTIS.Conclusions Non-thyroidal illness syndrome in elderly inpatients is correlated with advanced age,renal insufficiency,malnutrition and stress,which are the independent risk factors.