Relationship between Thyroid Function and Kidney Function in Patients with Type 2 Diabetes

Purpose. To determine if the TSH is related to estimated glomerular filtration rate (eGFR) in T2D patients without overt thyroid dysfunction. Methods. A cohort study of 5936 T2D patients was assessed for thyroid and kidney functions, in whom 248 with subclinical hyperthyroidism and 362 with subclinical hypothyroidism. Serum creatinine and 24-hour urine albumin excretion (UAE) were collected. Chronic kidney disease (CKD) was defined as eGFR < 60 ml/min/1.73 m(2). Results. Compared with euthyroid subjects, the patients with subclinical hypothyroidism had lower eGFR (82.7 +/- 22.4 vs. 90.5 +/- 22.4 ml/min/1.73 m(2), p < 0.01), higher UAE (114 +/- 278 vs. 88 +/- 229 mg/24 h, p < 0.05), and high incidence of CKD (16.0% vs. 10.1%, p < 0.05). The participants with a TSH level between 0.55 and 3.0 mu IU/ml had a higher eGFR (91.4 +/- 22.2 ml/min/1.73 m(2)) and a lower prevalence of CKD (9.5%) than those with higher TSH (3.01-4.78 mu IU/ml, 85.6 +/- 22.7 ml/min/1.73 m(2), p < 0.01 and 13.1%, p < 0.01). Linear logistic regression analysis showed that the eGFR was significantly negatively associated with TSH (OR: 0.519, 95% CI: 0.291-0.927, p < 0.05), after adjustment of confounders. Conclusion. High TSH was independently associated with decreased eGFR in type 2 diabetes patients without overt thyroid dysfunction. Our findings indicate that doctors who treat T2D patients should routinely measure the thyroid function.