Vitamin D status in Paget's bone disease. Effects of calcitonin therapy

In 15 patients suffering from Paget's disease, the serum levels of alkaline phosphatase (ALP), 25-hydroxycholecalciferol (25OHD3), 24,25-dihydroxycholecalciferol (24,25 [OH] 2D3), 1,25-dihydroxycholecalciferol (1,25 [OH] 2D3), and parathormone (PTH) as well as urinary excretion of hydroxyproline (HP) have been determined before and after three-month calcitonin therapy. Before therapy, high concentrations of serum ALP and urinary HP excretion had been observed, whereas serum levels of 24,25 (OH) 2D3 were below the lower limit of the normal range. Calcitonin therapy caused a 31% reduction in ALP and a 50% reduction in HP, as well as a significant increase in serum levels of 24,25 (OH) 2D3; the levels of 25OHD3, 1,25 (OH) 2D3, and PTH remained unchanged after treatment. The significant negative correlation between 24,25 (OH) 2D3 and ALP and HP before and after calcitonin therapy suggests that in Paget's disease there is an uncompensated increased bone usage of 24,25 (OH) 2D3.