Subclinical Hypothyroidism in Advanced Chronic Kidney Disease Patients: Prevalence and Associated Factors

INTRODUCTION: Renal function and thyroid metabolism are tightly related. However, evidence about subclinical hypothyroidism prevalence in patients with chronic kidney disease and its related factors is scarce. OBJECTIVES: Our aim is to analyze subclinical hypothyroidism prevalence and its related factors in patients with advanced chronic kidney disease. Materials and methods. Nondialysis-dependent patients with chronic kidney disease at stages 3 to 5 were included. Other inclusion criteria were age above 18 years and clinical stability. Patients with diagnosed thyroid illnesses were excluded. Subclinical hypothyroidism was defined as thyroid stimulating hormone (TSH) > 5.3 mU/L, with free thyroxine 4 (FT4) between 0.54 and 1.24 ng/dl. Filiation data, comorbidities, and routine blood and urine test results were registered. RESULTS: A total of 299 patients were included. Of them, 184 (61.5%) were men. The mean age was 71 ± 13 years old. The mean glomerular filtration rate (CKD-EPI) was 22 ± 9 ml/min/1.73 m(2). According to chronic kidney disease stages, global distribution of patients was as follows: Stage 3, 67 patients (22.4%); Stage 4, 155 patients (51.8%); and Stage 5, 77 patients (25.8%). We found subclinical hypothyroidism in 54 (18.1%) patients. According to chronic kidney disease stages, distribution of affected patients was as follows: Stage 3, 9 patients (13%); Stage 4, 25 patients (16.1%); and Stage 5, 20 patients (26%). Differences among stages were statistically significant. By univariate analysis, factors related with subclinical hypothyroidism were as follows: age RR 1.048 (95% CI 1.019–1.078; p=0.001), hypertension RR 2.705 (95% CI 1.026–7.130; p=0.04), glomerular filtration rate RR 0.962 (95% CI 0.929–0.996; p=0.03), and proteinuria higher than 1 gram/day RR 2.387 (95% CI 1.303–4.374; p=0.005). By multivariate analysis adjusted by age, hypertension, glomerular filtration rate, proteinuria, diabetes, and cardiovascular disease history, only age RR 1.016 (95% CI 1.009–1.028; p=0.04) and glomerular filtration rate RR 0.963 (95% CI 0.930–0.997; p=0.03) preserved their independent association with subclinical hypothyroidism. CONCLUSIONS: Subclinical hypothyroidism prevalence in patients with chronic kidney disease is high and increases with renal disease severity. Factors independently related to subclinical hypothyroidism are age and glomerular filtration rate.