Abstract
BackgroundPrevious studies have reported the relationship between thyroid hormone levels and mortality in dialysis patients. However, little is known about the association of free thyroxine (fT4) and mortality in patients on peritoneal dialysis (PD). This study investigated the association between basal and annual variation in fT4 level and mortality in PD patients.MethodsPatients on maintenance PD were enrolled from a prospective multicenter cohort study in Korea; their serum triiodothyronine, fT4, and thyroid-stimulating hormone levels were measured 12 months apart. Patients with overt thyroid disease and those receiving thyroid hormone replacement therapy were excluded from the analysis. Patients were divided into two groups based on the median levels of fT4. The differences of all-cause, infection-related, and cardiovascular mortalities were analyzed between the two groups. The association of basal levels and annual variation with mortality was investigated with Kaplan–Meier curves and Cox proportional hazard models.ResultsAmong 235 PD patients, 31 (13.2%) deaths occurred during the mean follow-up period of 24 months. Infection (38.7%) was the most common cause of death. Lower basal fT4 levels were an independent predictor of all-cause and infection-related death (hazard ratio [HR] = 2.74, 95% confidence interval [CI] 1.27–5.90, P = 0.01, and HR = 6.33, 95% CI 1.16–34.64, P = 0.03, respectively). Longitudinally, patients with persistently lower fT4 levels during the 12-month period had significantly higher all-cause mortality than those with persistently higher levels (HR = 3.30, 95% CI 1.15–9.41, P = 0.03). The area under the receiver operating characteristic curve of fT4 for predicting all-cause and infection-related mortality was 0.60 and 0.68, respectively.ConclusionsfT4 level is an independent predictor of mortality and is especially attributable to infection in PD patients. This predictor was consistent when considering both baseline measurements and annual variation patterns. Close attention to infection in PD patients with relatively lower fT4 levels should be considered.
Highlights
End-stage renal disease (ESRD) is a frequent cause of altered thyroid hormone levels in the absence of underlying intrinsic thyroid disorder
Lower basal fT4 levels were an independent predictor of all-cause and infection-related death
Lower fT4 levels showed, albeit not significantly, a trend for increased infection-related mortality (Table 4). This multicenter prospective cohort study shows the association of low fT4 levels with higher mortality rates in maintenance peritoneal dialysis (PD) patients
Summary
End-stage renal disease (ESRD) is a frequent cause of altered thyroid hormone levels in the absence of underlying intrinsic thyroid disorder. Several studies suggested that as many as 70% of patients with ESRD presented with low T3 levels and as many as 20–25% had subclinical hypothyroidism [2, 3]. These alterations reflects iodine retention, diminished conversion of T4 to T3 in the periphery, reduced serum protein-binding capacity [1], and metabolic acidosis [4] in patients with ESRD. Recent reports about dialysis patients have suggested that low T3 levels and subclinical hypothyroidism are associated with higher cardiovascular and all-cause mortality [5,6,7,8]. The association of basal levels and annual variation with mortality was investigated with Kaplan–Meier curves and Cox proportional hazard models
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