Parathyroid hormone, calcitonin and vitamin D metabolites in beta-thalassaemia major.

Serum calcium (Ca), phosphorus (P), alkaline phosphatase (Al-P), parathyroid hormone (PTH), calcitonin (CT), 25-hydroxyvitamin D3 (25OHD3), 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) levels and urinary excretion of Ca, P, hydroxyproline (OH-P) and cyclic AMP (cAMP) were determined in summer and in winter in 13 thalassaemic children (7 aged 3-5 years-group 1-; and 6 aged 10-13 years-group 2-), who had never taken vitamin D supplements or therapy, and in two groups of 14 controls of the same age. In thalassaemics of group 1 only serum Al-P levels and OH-P urinary excretion were higher than in controls (P less than 0.01). In thalassaemics of group 2 Ca (P less than 0.05), P (P less than 0.05), PTH (P less than 0.001), CT (P less than 0.001), 25OHD3 (P less than 0.05), 1,25(OH)2D3 (P less than 0.001) levels and cAMP urinary excretion (P less than 0.001) were lower, whereas Al-P (P less than 0.001) and CT (P less than 0.001) levels and urinary excretion of P (P less than 0.05) and of OH-P (P less than 0.001) were higher than in controls, both in summer and in winter. Advancing age induces in thalassaemic patients a decrease in PTH secretion and a consequent deficit in synthesis of 1,25(OH)2D3 that may explain some aspects of bone changes, which CT hypersecretion may tend to counteract.