BACKGROUND: Hypothyroidism is a common endocrine disorder with a bi-directional relationship to Chronic Kidney Disease (CKD), presenting a notable complication in CKD patients. This study aimed to explore the impact of hypothyroidism on kidney function in CKD patients. MATERIALS AND METHODS: This study included 150 participants, with 110 CKD patients without hypothyroidism and 40 CKD patients with hypothyroidism. The participants were further categorized into stages 3, 4, and 5 based on their estimated Glomerular Filtration Rate (eGFR). They were followed for three consecutive months at intervals of 28 ± 3 days, 57 ± 3 days, and 86 ± 3 days. Clinical and demographic data, including age, gender, serum creatinine, serum urea, Blood Urea Nitrogen (BUN), eGFR, and serum sodium, potassium, and chloride levels, were assessed over time. Data analysis was performed using GraphPad Prism, with a significance level set at 0.05%. RESULTS: In CKD patients with hypothyroidism, serum creatinine (P = 0.0002), serum urea (P = 0.0046), and BUN (P = 0.0042) levels were significantly higher, while eGFR (P <
0.0001) was lower compared to CKD patients without hypothyroidism. Potassium levels were significantly elevated in CKD patients with hypothyroidism (P = 0.0001), whereas no significant difference was observed in serum sodium (P = 0.0802) or chloride (P = 0.2089) levels. CONCLUSION: This study concludes that CKD patients with hypothyroidism experience a more significant decline in kidney function compared to CKD patients without hypothyroidism.