Background/aim: Renal function of patients with hypothyroidism increases after reaching euthyroid state. There is no data regarding geriatric age group. The aim of the study was determined to investigate whether renal function of geriatric patients with hypothyroidism increases after they become euthyroid. Materials and methods: Patients who were sixty-five years or older were retrospectively screened in two centers. TSH, T3, T4, creatinine, and eGFR calculated by CKD-EPI formula were recorded under the presence of accompanying hypothyroidism. The same variables were recorded after the patients became euthyroid. Results: 285 patients were included in the study, the median age was 73(65–84), and 234 patients were female. Patients were examined in four groups according to TSH values. There were 160 (56.1%) patients with TSH 5–9.9 uIU/mL, 60(21.1%) patients with TSH between 10–19.9 uIU/mL, 41(14.4 %) patients with TSH between 20–49.9 uIU/mL and 24(8.4%) patients with TSH> 50uIU/mL. There was a significant and negative correlation between the initial TSH values and the first calculated eGFR values (p: 0.001; r: –0.191). The median eGFR of the patients in hypothyroid cases was 66.59 (14.62–116.07), while the median eGFR value of patients was 69.6 (12.91–109.31) in the euthyroid state. This value obtained after thyroid replacement was significantly improved when compared to the first eGFR (p: 0.001). In logistic regression analysis, pretreatment TSH value was found to independently affect eGFR (p: 0.009; Exb: 1.017). Conclusion: It has been observed that hypothyroidism treatment increases eGFR in geriatric patients. Similar results were obtained after studies with younger patients in the literature. This study is a study in which only geriatric age group patients were examined. It should be kept in mind that hypothyroidism which is not corrected in geriatric patients may also contribute to a decrease in eGFR.Key words: Hypothyroidism, older, renal