Association between serum homocysteine and kidney function in hypothyroid patients: A case-control study in Northeast Iran.

Background/objectives: The relationship between serum homocysteine (Hcy) and kidney function in hypothyroidism is not fully understood. This case-control study investigated the association of hyperhomocysteinemia (HHcy) with kidney function tests in patients diagnosed with clinical hypothyroidism (CH). Methods: Forty-five CH cases and 45 matched controls were recruited from a referral clinic in northeast Iran. Serum Hcy was measured using ELISA technology, and Spearman's correlation coefficients were estimated to assess the association between Hcy and various kidney function parameters. Results: In CH patients, the average Hcy level was significantly higher than in those with normal thyroid function (22.63 ± 1.21 vs 12.96 ± 0.24 μmol/L, p = 0.001). Among CH patients, 82.2 % had HHcy (60 % mild, 12.2 % moderate), while only 13.3 % of controls had mild HHcy. Hcy levels were positively correlated with TSH (r = 0.528; p = 0.001), eGFR (r = - 0.418; p = 0.004), urea (r = 0.371; p = 0.012), and creatinine (r = 0.384; p = 0.009) in CH patients. Multivariate logistic regression revealed a significant relationship between Hcy and CH [OR = 2.01, 95 % CI: 1.48-2.72, p = 0.001], even after adjusting for kidney parameters. Conclusions: Serum Hcy was increased with progressive thyroid insufficiency, independent of changes in kidney function, and could be considered a potential risk factor for developing coronary heart disease.