Molecular basis for the management of secondary hyperparathyroidism in chronic renal failure

[Oral calcitriol pulse therapy in hemodialysis patients. Effects on histomorphometry of bone in renal hyperparathyroidism]

BACKGROUND

Hemodialysis patients with symptomatic renal hyperparathyroidism should only get a surgical parathyroidectomy if the oral calcitriol pulse therapy fails. Unfortunately there is no general accepted recommendation for the dosage and intervals of the oral calcitriol pulse therapy.

PATIENTS AND METHODS

In 34 hemodialysis patients (9 women, 25 men, mean age: 50 +/- 13 years, mean duration time of dialysis: 20 +/- 30 months) with renal hyperparathyroidism (intact parathormon = iPTH > 20 pmol/l) an oral calcitriol pulse therapy was performed over a period of one year. The initial dosage of calcitriol was 0.1 microgram/kg bwt a week, splitted into two equal dosages given at night. After 3 months the calcitriol dosage was changed according to the iPTH, calcium and phosphate levels. The dialysate calcium concentration was kept constant with 1.5 mmol/l. Before and after one year a bone biopsy was performed. The target level for a successful treatment was < or = 20 pmol/l.

RESULTS

In the group of responders (n = 24) the iPTH level decreased significantly (p < 0.01) from 37.5 +/- 3.2 to 14.3 +/- 1.9 pmol/l after a period of 12 months. There was no significant change of the iPTH levels in the 10 non-responders (55.5 +/- 6.5 vs 57.2 +/- 9.7 pmol/l). The incidence of hypercalcemia was higher in the non-responder group (19.2%) as compared to the responder group (13.4%). In the group of responders the bone resorption decreased, whereas the bone formation increased under an oral calcitriol pulse therapy.

CONCLUSION

A decrease in iPTH level in hemodialysis patients undergoing an oral calcitriol pulse therapy with an initial dosage of 0.1 microgram/kg bwt. was found in 71% of the patients after one year. Calcitriol improves the histomorphometrical parameters in responders.