Switch from calcitriol to paricalcitol insecondary hyperparathyroidism ofhemodialysis patients: Responsiveness isrelated to parathyroid gland size

Paricalcitol is more effective than calcitriol in hemodialysis patients (HD) with secondary hyper-parathyroidism (SHPT), but it is not effective in some of them. We have investigated the relationshipbetween paricalcitol responsiveness and parathyroid gland (PTG) size. Thirty HD with SHPT treatedpreviously with calcitriol for at least 6 months were switched to paricalcitol (1:4 conversion ratio).Parathyroid gland number and size (maximum longitudinal diameter [MLD] of largest PTG) wasmeasured by ultrasonography. Patients were divided into 2 groups: group A (MLD9.0mm [17HD]); and group B (MLD49.0mm [13 HD]). They were defined responder if both the last 2 monthlydeterminations of inhibit parathyroid hormone (iPTH) were within the target (o300pg/mL) accord-ing to National Kidney Foundation Kidney Disease Outcomes Quality Initiative recommendations.Twenty-six and 20 HD completed 6-month and 12-month paricalcitol therapy, respectively. After 6months of paricalcitol treatment, 23.5% HD of group A and 7.7% of group B were responders. At 12months, 41.2 % of group A and 7.7% of group B were responders. Throughout paricalcitol therapy,serum calcium and phosphorus concentrations slightly increased in all HD but more significantly ingroup B. The baseline iPTH and MLD of the largest PTG were significantly correlated with final iPTHlevels.Paricalcitol is more effective than calcitriol in SHPT, but the responsiveness to paricalcitol andhypercalcemia are related to PTG size. The measurement of MLD by ultrasonography may be usefulfor predicting responsiveness to paricalcitol, avoiding an unnecessary and expensive therapy.