Abnormal thyroid function predicts mortality in patients receiving long-term peritoneal dialysis: A case-controlled longitudinal study

Background: The population of uremia patients receiving long-term peritoneal dialysis (PD) is growing, and abnormal thyroid function occurs increasingly in patients with chronic kidney disease in comparison with the normal population. We aimed to elucidate the clinical impact of abnormal thyroid function in long-term PD patients. Methods: This was a retrospective, case-controlled, longitudinal study. We collected the characteristics, laboratory data, dialysis parameters, and thyroid and heart function of patients who underwent long-term PD for >8 years during the past 25 years in Taipei Veterans General Hospital, Taiwan. Patients with hyperthyroidism were excluded. None of these subjects presented a recent history of infection or inflammatory disease or took any drugs known to influence thyroid function. Abnormal thyroid function was defined as the presence of primary hypothyroidism and sick euthyroid syndrome. Results: A total of 46 patients were enrolled. The mean duration of PD therapy was 147.8 (48.3) months. Nineteen of 46 (41.3%) patients had abnormal thyroid function tests. Patients with abnormal thyroid function had a worse prognosis in cumulative patient survival analysis by Kaplan-Meier method (p = 0.02). After adjusting for diabetes mellitus, cardiothoracic ratio, C-reactive protein (CRP), and cardiovascular diseases, abnormal thyroid function remained as an independent predictor of patient survival (hazard ratio = 7.633, 95% confidence interval 1.3-43.9, p = 0.02). The CRP levels were significantly inversely correlated with free thyroxine levels (r = -0.547; p = 0.01). The most common cause of death among the patients was sepsis (67.7%) rather than cardiovascular disease (20.0%). Conclusion: PD patients with abnormal thyroid function had poor cumulative survival. Lower thyroid hormone level in PD patients was associated with high CRP levels. Physicians should be alert for the presence of abnormal thyroid function and proinflammatory status in long-term PD patients.