Biological activity of endogenous and exogenous calcitonin in patients with osteitis fibrosa and chronic renal failure.

Successful treatment of osteitis fibrosa with 1alpha-hydroxycholecalciferol (1alpha-OHD3) in 9 patients with end-stage chronic renal failure was associated with a significant increase in plasma levels of immunoreactive calcitonin (iCT) independently of changes in plasma calcium, and a decrease in levels of parathyroid hormone (iPTH). In 9 further patients whose plasma alkaline phosphatase activity failed to suppress with 1alpha-OHD3, changes in iPTH were associated with proportionate changes in iCT. This suggests that a rise in endogenous calcitonin (CT) secretion contributes to the success of treatment with 1alpha-OHD3. In 13 further patients, injections of salmon CT induced a fall in plasma calcium and phosphate which was proportional to the prevailing level of plasma alkaline phosphatase. These data provide further evidence that bone resorption can be effectively inhibited when CT levels are raised either by exogenous CT or its endogenous stimulation.