Unresolved Subclinical Hypothyroidism is Independently Associated with Progression of Chronic Kidney Disease

Background and Aim: Patients with chronic kidney disease (CKD) often have subclinical hypothyroidism. However, few reports have investigated changes in the status of subclinical hypothyroidism in CKD patients and its clinical significance in CKD progression. Methods: We included 168 patients with nondialysis-dependent CKD stages 2-4. The normalization of subclinical hypothyroidism during follow-up was assessed, and the association between transitions in subclinical hypothyroid status and the rate of decline of the estimated glomerular filtration rate (eGFR) was investigated. Results: At baseline, 127 patients were euthyroid and 41 (24.4%) patients were diagnosed with subclinical hypothyroidism. Of these 41 patients, 21 (51.2%) spontaneously resolved to euthyroid during follow-up. The rate of eGFR decline of patients with resolved subclinical hypothyroidism was similar to that of euthyroid patients. The patients with unresolved subclinical hypothyroidism showed a steeper renal function decline than patients with euthyroidism or resolved subclinical hypothyroidism (all p < 0.05). The progression to end-stage renal disease was more frequent in those with unresolved subclinical hypothyroidism than in those who were euthyroid (p = 0.006). In multivariate linear regression for rate of eGFR decrease, unresolved subclinical hypothyroidism (β = -5.77, p = 0.001), baseline renal function (β = -0.12, p < 0.001) and level of proteinuria (β = -2.36, p = 0.015) were independently associated with the rate of renal function decline. Conclusions: Half of the CKD patients with subclinical hypothyroidism did not resolve to euthyroidism, and this lack of resolution was independently associated with rapid renal function decline.