A trial of suppressing secondary hyperparathyroidism by oral high dose therapy of 1, 25-dihydroxyvitamin D₃

We reported a successful treatment of secondary hyperparathyroidism by intermittent oral administration of high dose of 1, 25 dihydroxycholecalciferol [1.25-(OH)₂D₃] in three patients on maintenance hemodialysis. Dialysis durations were 4 months in case 1,6.5 tears in case 2 and 12.5 years in case 3. The leveis of c-PTH ranged from 47 ng/ml to 94.2 ng/ml. 1,25-(OH)₂D₃ in dosages upto 8.0 µg was given once a week just after hemodialysis Before the adminitration and after 48 hours, serum Ca, serum Pi, serum Mg, c-PTH and highly sensitive PTH were assayed. There was a significant correlation between max. plasma concentration of 1, 25-(OH)₂D and logarithm of the dose in all patients. The max. plasma level of 1, 25-(OH)₂D reached to 200 pg/ml at 4 hours after the oral administration of 8.0 µg. Their thresholds of 1,25-(OH)₂D level which could decrease the PTH levels were elevated proportionally to their dialysis durations. Case 1 required 4.0µg to suppress secondary hyperparathyroidism, whereas, case 2 and 3 did 8 0 µg of 1, 25-(OH)₂D₃. Severe hypercalcemia was not observed during a high dose treatmeut. In conclusion, we have succeeded in treating refractory secondary hyperparathyroidism by intermittent oral administration of high dose 1,25-(OH)₃D₃. This therapy is recommended to start in the earlier stage of a long-term dialysis in oder to prevent severe secondary hyperparathyroidism and bone disease.