[Disturbances of calcium-PTH-vitamin D axis in chronic liver diseases]

Disturbances in Calcium-PTH-Vitamin D axis are frequently associated with chronic liver diseases (CLD). In patients with CLD, a trend toward decreased serum calcium and vitamin D has already been demonstrated with compensatory increases in PTH levels. Even though reduced vitamin D hydroxylation has been considered the most important mechanism for these alterations, recent studies demonstrates an adequate production of 25(OH) Vitamin D even in end-stage liver disease. Therefore, other factors (i.e. inadequate diet, reduced exposure to sun light) would be responsible for the disturbances in calcium-PTH-vitamin D axis. Furthermore, antiviral drugs (such as ribavirin for hepatitis C) and glucocorticoids (cystic fibrosis) may also contribute to the worsening of these disturbances. On the other hand, osteoporosis, but not osteomalacia or secondary hyperparathyroidism, seems to be the main alteration in CLD. Thus, the clinical relevance of calcium-PTH-vitamin D disturbances in hepatic osteodystrophy is still under discussion.