Thyroid hormone replacement therapy attenuates the decline of renal function in chronic kidney disease patients with subclinical hypothyroidism.

BACKGROUND: Subclinical hypothyroidism (SCH) is not a rare condition in females, the elderly, or patients with chronic kidney disease (CKD). Even though previous studies have demonstrated that thyroid hormone replacement therapy (THRT) improves cardiac function and dyslipidemia in patients with SCH, it remains unclear as to whether THRT can improve renal function in CKD patients with SCH. This study investigated the impact of THRT on changes in estimated glomerular filtration rates (eGFR) in this patient population.

METHODS: A total of 113 CKD patients with SCH who were treated with L-thyroxine and had eGFR available for at least 24 months before and after THRT were enrolled between January 2005 and December 2011. A linear mixed model was used to compare patients' clinical and biochemical parameters at various time points. The slope of the decline in eGFR over time, both before and after THRT, was also calculated and compared using a linear mixed model.

RESULTS: The mean age of the study participants was 63.2±12.7 years, and 36 patients (31.9%) were men. The mean follow-up duration before and after THRT was 28.6±4.5 and 30.6±6.4 months respectively. After 24 months of THRT, serum thyrotropin (TSH) levels were significantly reduced-8.86±0.49 versus 1.41±0.73 μIU/mL, p<0.001-but there were no significant changes in triiodothyronine and free thyroxine concentrations. Serum albumin, calcium, phosphate, cholesterol, and triglyceride levels were also comparable before and after THRT. The rates of decline in eGFR were significantly attenuated by THRT (-4.31±0.51 vs.-1.08±0.36 [mL/min]/[year·1.73 m²], p<0.001), even after adjustment for age, sex, diabetes, mean arterial pressure, and serum albumin, cholesterol, and triglyceride concentrations (p<0.001).

CONCLUSION: THRT attenuated the rate of decline in renal function in CKD patients with SCH, suggesting that THRT may delay reaching end-stage renal disease in these patients.