MDPI Acta Medica Okayama 2075-4418 13 4 2023 Association between Urinary Creatinine Excretion and Hypothyroidism in Patients with Chronic Kidney Disease 669 EN Natsumi Matsuoka-Uchiyama Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kenji Tsuji Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kensaku Takahashi Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kazuhiko Fukushima Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Hidemi Takeuchi Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Shinji Kitamura Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kenichi Inagaki Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Haruhito A. A. Uchida Department of Chronic Kidney Disease and Cardiovascular Disease, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Jun Wada Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences While hypothyroidism increases serum creatinine (Cr) levels, it is uncertain whether the elevation is mediated via a decline in the glomerular filtration rate (GFR) or the reflection of enhanced Cr production from the muscles or both. In the present study, we explored an association between urinary Cr excretion rate (CER) and hypothyroidism. A total of 553 patients with chronic kidney disease were enrolled in a cross-sectional study. Multiple linear regression analysis was performed to explore the association between hypothyroidism and urinary CER. The mean urinary CER was 1.01 +/- 0.38 g/day and 121 patients (22%) had hypothyroidism. The multiple linear regression analysis revealed explanatory variables with urinary CER, including age, sex, body mass index, 24 h Cr clearance (24hrCcr), and albumin while hypothyroidism was not considered an independent explanatory variable. In addition, scatter plot analysis with regression fit line representing the association between estimated GFR calculated using s-Cr (eGFRcre) and 24hrCcr revealed that eGFRcre and 24hrCcr had strong correlations with each other in hypothyroid patients as well as euthyroid patients. Collectively, hypothyroidism was not considered an independent explanatory variable for urinary CER in the present study and eGFRcre is a useful marker to evaluate kidney function regardless of the presence of hypothyroidism. No potential conflict of interest relevant to this article was reported.