#442 Hyperparathyroidism, serum phosphorus and dietary intake in hemodialysis patients: is there a novel relationship?

Abstract Background and Aims Hyperparathyroidism (HPTH), classified when intact parathyroid hormone (iPTH) serum levels are above 585 pg/mL, is a common complication in patients undergoing maintenance hemodialysis (HD). Despite there is little evidence about the relationship between iPTH levels and nutritional status, the intervention frequently focusses on appropriate management of mineral and bone markers, being the decrease of serum and dietary phosphorus some of the targets. The aim of this study was to investigate the association between iPTH, serum phosphorus levels and dietary intake. Method This was a cross-sectional, multicenter, observational study with 561 patients on HD treatment from 37 dialysis centers across Portugal. Clinical parameters, body composition and dietary intake (obtained from a Food Frequency Questionnaire) were assessed. For the analysis, patients were divided in 3 groups depending on their iPTH levels: a) iPTH<130, b) iPTH between 130-585 and c) iPTH >585 pg/mL. The association between PTH, serum phosphorus and dietary intake was analyzed with linear regression models. A p-value lower than 0.05 was considered statistically significant. Results Patients’ mean age was 68 ± 14 years, median HD vintage was 65 (IQR: 43-106) months and 58.8% were men. From the whole sample, 13.9% presented a iPTH <130 pg/mL, 59.3% between 130-585 pg/mL and 23.2% >585 pg/mL. Patients with higher iPTH levels were those with longer HD vintage (p = 0.021) and lower age (p = 0.002). At the same time, showed higher serum phosphorus (p = 0.005), serum calcium (p = 0.027), Ca/P product (p < 0.001), albumin (p = 0.016) and caffeine intake (p = 0.009). In addition, a lower dietary intake of phosphorus (p = 0.044), fiber (p = 0.047), riboflavin (p = 0.031) and folate (p = 0.011) were observed in patients with higher iPTH levels. In the linear regression models, higher serum phosphorus predicted higher iPTH levels, even in the adjusted model (p = 0.019). However, a lower phosphorus intake was a predictor of higher iPTH levels, also in the model adjusted to age, gender, serum phosphorus, dialysis adequacy (Kt/V) and dialysis vintage (p = 0.035). The same result was observed when considering the dietary fiber intake in the model (p = 0.048). No significant differences in body composition parameters were found. Conclusion Our results bring new data on the relationship between dietary intake and iPTH values. Despite higher serum phosphorus was observed in patients with HPTH, an opposite association was noted regarding dietary phosphate and fiber as lower intakes predicted higher iPTH values. Moreover, a poorer dietary intake, considering riboflavin and folate was observed in the HPTH group.