Thyroid Functional Disease and Mortality in a National Peritoneal Dialysis Cohort

Abstract

Context and Objective: End-stage renal disease patients have a higher risk of thyroid disease compared with those without kidney disease. Although thyroid dysfunction is associated with higher death risk in the general population and those undergoing hemodialysis, little is known about the effect of thyroid disease upon mortality in patients treated with peritoneal dialysis (PD). Design, Setting, Participants, and Main Outcome: We examined the association of thyroid status, assessed by serum TSH, with all-cause mortality among PD patients from a large national dialysis organization who underwent one or more TSH measurements over 5 years (January 2007 to December 2011). Thyroid status was categorized as overt-hyperthyroid, subclinical-hyperthyroid, low-normal, high-normal, subclinical-hypothyroid, and overt-hypothyroid range (TSH < 0.1, 0.1–<0.5, 0.5–<3.0, 3.0–<5.0, 5.0–<10.0, and ≥10.0 mIU/L, respectively). We examined the association between TSH and mortality using case mix–adjusted time-dependent Cox models to assess short-term thyroid function–mortality associations and to account for changes in thyroid function over time. Results: Among 1484 patients, 7 and 18% had hyperthyroidism and hypothyroidism, respectively, at baseline. We found that both lower and higher time-dependent TSH levels were associated with higher mortality (reference: TSH, 0.5–<3.0 mIU/L): adjusted hazard ratios (95% confidence intervals) 2.09 (1.08–4.06), 1.53 (0.87–2.70), 1.05 (0.75–1.46), 1.63 (1.11–2.40), and 3.11 (2.08–4.63) for TSH levels, <0.1, 0.1–<0.5, 0.5–<3.0, 3.0–<5.0, 5.0–<10.0, and ≥10.0 mIU/L, respectively. Conclusion: Time-dependent TSH levels < 0.1 mIU/L and ≥ 5.0 mIU/L were associated with higher mortality, suggesting hyper- and hypothyroidism carry short-term risk in PD patients. Additional studies are needed to determine mechanisms underlying the thyroid dysfunction–mortality association, and whether normalization of TSH with treatment ameliorates mortality in this population.