Risk factors and risk for mortality of mild hypoparathyroidism in hemodialysis patients

Abstract

Relative hypoparathyroidism (parathyroid hormone [PTH] < or = 200 pg/mL) is prevalent in hemodialysis (HD) patients, with unknown pathogenesis and prognosis. Thus, to clarify risk factors and prognosis of time-dependent relative hypoparathyroidism in HD patients, a retrospective cohort study was performed for 126 HD patients with four or more PTH determinations and no previous total or subtotal parathyroidectomy. Values for intact PTH, ionized calcium, phosphate, magnesium, albumin, creatinine, urea reduction ratio (URR), glucose, hemoglobin A1c (HbA1c), aluminum, and 1,25(OH)2D were obtained at enrollment and at some time during follow-up. The prevalence of relative hypoparathyroidism at entry was 76 of 126 patients (60.3%). Univariate analysis showed that patients with hypoparathyroidism were older, more likely to have diabetes, and had greater ionized calcium levels and lower phosphate, albumin, blood urea nitrogen (BUN), and creatinine levels. Patients with diabetes were older and had a shorter duration of dialysis therapy and lower PTH, phosphate, albumin, BUN, and creatinine levels and URRs. Conversely, multivariate analysis showed that PTH levels at entry were associated directly with creatinine levels and inversely with age and ionized calcium levels (but not diabetes). During follow-up, PTH levels fluctuated concomitantly with ionized calcium and phosphate levels over time in all patients. Time-dependent PTH levels were associated directly with duration of dialysis therapy and use of vitamin D and phosphate and albumin levels, but inversely with age and ionized calcium and magnesium levels (but not glucose or HbA1c levels). Interestingly, time-dependent PTH levels were independently associated with survival after adjusting for traditional risk factors (diabetes, age, albumin and creatinine levels, and URR) and duration of dialysis therapy. We conclude that in HD patients, relative hypoparathyroidism was not associated with diabetes per se. Time-dependent PTH levels were associated with age, duration of dialysis, and levels of ionized calcium, phosphate, albumin, and magnesium. Moreover, relative hypoparathyroidism at entry and lower time-dependent PTH levels predict mortality.