Disturbed calcium metabolism in renal failure--pathogenesis and therapeutic strategies

Absolute or relative deficiency of 1,25(OH)2 vitamin D3 is thought to play a key role in the genesis of secondary (renal) hyperparathyroidism. Elevated concentrations of PTH and--less consistently--diminished concentrations of 1,25(OH)2 vitamin D3 are demonstrable in a considerable proportion of patients with incipient renal failure. Increased PTH concentrations counteract to some extent the trend of 1,25(OH)2 vitamin D3 production to decrease. When iPTH is elevated, prophylactic administration of 1,25(OH)2 vitamin D3 is a logical procedure, even when patients have not yet reached end-stage renal failure. With the use of low doses, the incidence of side effects is low, and excessive lowering of PTH and bone turnover presumably can be avoided. Acute administration of 1,25(OH)2 vitamin D3 to achieve brief episodes of peak plasma levels causes prolonged suppression of pre-pro-PTH mRNA in the parathyroid cell. This provides a rationale to treat symptomatic hyperparathyroidism with intermittent high dose 1,25(OH)2 vitamin D3, either per os or i.v.