Suppression of hyperparathyroidism by calcitriol therapy

We reviewed the charts of 160 patients on hemodialysis and identified 33 wi th parathyroid hormone (PTH) > 800 pg/ml at any time during the last 3 year s to confirm our impression that patients with PTH elevations for short dur ations of time require significantly smaller doses of calcitriol than those with prolonged PTH elevations, We divided the patients into two groups: 18 with PTH > 800 pg/ml on three or fewer occasions (Group 1, short-term hype rparathyroidism) and 15 with PTH > 800 pg/ml more than three times (Group 2 , long-term hyperparathyroidism). Most patients received once weekly intrav enous calcitriol, but if this failed to suppress PTH, the dose was increase d gradually to three limes a week, PTH was measured at mid-week, calcitriol was held if serum calcium rose to >11 mg/dl, and calcitriol was started ag ain when calcium fell to <11 mg/dl, We found that the duration of dialysis was generally shorter in Group 1, as were maximal PTH levels. Calcitriol su ppressed PTH levels to <200 pg/ml in both groups, However, the weekly dose of calcitriol needed to suppress PTH was significantly lower in Group 1 (5. 4 +/- 1.2 mu g in Group 1 and 11.4 +/- 1.8 mu g in Group 2; p < 0.001). Fur ther follow-up of seven patients for 1 more year showed continued suppressi on of PTH, and the dose of calcitriol required to maintain the suppression was lower than the initial dose, Thus patients with longer histories of dia lysis and prolonged hyperparathyroidism required higher doses of calcitriol to suppress PTH to the same level as patients who were new on dialysis or with transient hyperparathyroidism, A protocol of three times weekly, high dose calcitriol with strict monitoring of serum calcium will avoid parathyr oidectomy in most cases.