Subclinical hypothyroidism is independently associated with poor renal outcomes in patients with chronic kidney disease

Purpose: It remains unclear whether subclinical hypothyroidism (SCH) is associated with renal prognosis in patients with chronic kidney disease (CKD). Therefore, we prospectively investigated the association of SCH with renal outcomes in CKD. Methods: We conducted a prospective observational study of 480 euthyroid patients and 89 patients with SCH. The endpoints were defined as a composite of doubling of serum creatinine (SCr), end-stage renal disease (ESRD), or death, and a composite of doubling of SCr or ESRD was added as an alternative outcome. Logistic regression analyses were used to identify the factors associated with SCH. In addition, a Cox proportional hazards model was performed to determine whether SCH was associated with poor renal outcomes. Results: During a median follow-up period of 26.1 months, doubling of SCr, ESRD, or death and doubling of SCr or ESRD occurred in 244 and 213 patients, respectively. In univariable logistic regression analyses, SCH was significantly associated with older age, lower hemoglobin, higher proteinuria, lower estimated glomerular filtration rate (eGFR), and higher log B-type natriuretic peptide (BNP). Multivariable Cox analyses showed that SCH was associated with poorer renal outcomes after adjustment for covariates, including eGFR and log BNP [doubling of SCr, ESRD, or death: hazard ratio (HR) 1.61, 95% confidence interval (CI), 1.16–2.23; doubling of SCr or ESRD: HR 1.53, 95% CI 1.07–2.20], compared with euthyroidism. Conclusions: In CKD, SCH is independently associated with poor renal outcomes, suggesting that screening for SCH might be needed to accurately predict renal prognosis.