Background: Thyroid dysfunction is prevalent among elderly patients who had chronic kidney disease (CKD) due to metabolic and hormonal disturbances. This study aimed to evaluate thyroid dysfunction among elderly CKD patients with declining glomerular filtration rate (GFR). Methods: This prospective case-control study was conducted at Zagazig General Hospitals for one year. Sixty subjects (≥65 years) were divided into three groups: control (n=20), CKD stage III/IV (n=20), and hemodialysis (HD) (n=20). Clinical assessment, routine labs, eGFR calculation, thyroid function tests (T3, T4, fT3, fT4, TSH) via enzyme-linked immunoassay (ELISA) were performed. Results: Both CKD HD had blood pressure significantly higher than controls (p<0.05). Hemoglobin concentrations showed a decrease among CKD as well as the HD groups (p<0.001). Liver function markers (total protein, albumin, AST, ALT) were lower among the patient group considerably (p<0.05). Serum creatinine urea were found significantly higher in addition to a significant decline (p<0.001) in eGFR in the groups with CKD HD. T3 fT3 were considerably lower in CKD HD groups (p<0.001); however, non-statistical significant differences were found for TSH, T4, and fT4. CKD and HD subjects had higher prevalence rates of subclinical hypothyroidism and NTIS, displaying correlation with eGFR and hemoglobin, creatinine and urea levels. Conclusion: The study demonstrates a significant association between declining renal function and reduced T3/fT3 levels in elderly CKD patients, particularly among those undergoing hemodialysis. The findings underscore a higher prevalence of subclinical hypothyroidism and non-thyroidal illness syndrome in advanced stages of CKD, emphasizing the clinical importance of regular thyroid function monitoring