title: Free thyroxine level as an independent predictor of infection-related mortality in patients on peritoneal dialysis: a prospective multicenter cohort study.
abstract: BACKGROUND
  Previous 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.
  
  
  METHODS
  Patients 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.
  
  
  RESULTS
  Among 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.
  
  
  CONCLUSIONS
  fT4 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.
authors.affiliation: Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea.
authors.forename: Hee-Yeon
authors.initials: HY
authors.lastname: Jung
authors.affiliation: Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea.
authors.forename: Jang-Hee
authors.initials: JH
authors.lastname: Cho
authors.affiliation: Department of Statistics, Kyungpook National University, Daegu, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea.
authors.forename: Hye Min
authors.initials: HM
authors.lastname: Jang
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea.
authors.forename: Yon Su
authors.initials: YS
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea.
authors.forename: Shin-Wook
authors.initials: SW
authors.lastname: Kang
authors.affiliation: Department of Internal Medicine, The Catholic University of Korea College of Medicine, Seoul, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea.
authors.forename: Chul Woo
authors.initials: CW
authors.lastname: Yang
authors.affiliation: Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea.
authors.forename: Nam-Ho
authors.initials: NH
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea.
authors.forename: Ji-Young
authors.initials: JY
authors.lastname: Choi
authors.affiliation: Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea.
authors.forename: Sun-Hee
authors.initials: SH
authors.lastname: Park
authors.affiliation: Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea.
authors.forename: Chan-Duck
authors.initials: CD
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu, Korea; Clinical Research Center for End Stage Renal Disease, Daegu, Korea; Bk21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, Kyungpook National University, Daegu, Korea.
authors.forename: Yong-Lim
authors.initials: YL
authors.lastname: Kim
mesh_terms: D015331:Cohort Studies; D005260:Female; D006801:Humans; D007239:Infections / Q000097:blood* / Q000150:complications / Q000401:mortality* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis / Q000401:mortality*; D011446:Prospective Studies; D013960:Thyroid Function Tests; D013974:Thyroxine / Q000097:blood*
chemical_list: D013974:Thyroxine