[Role of diet in the management of osteodystrophy during progressive renal insufficiency]

Secondary hyperparathyrodism (SH) is an early manifestation of chronic renal failure (CRF), which has serious complications. Moreover, treating SH is not a risk-free process. Once in its advanced state, it is extremely difficult to reverse and therefore it is critical an early intervention and prevention. An excess of phosphorus and a deficit of calcium and calcitriol are key factors in the evolution of SH. Despite the fact that plasma phosphorus levels remain normal until an extremely advanced stage of CRF, and even apparent hyperphosphatemia in mild CRF, it has been shown that restricting dietary levels of protein and phosphorus impedes the progression of SH. A decrease of protein in the diet also decreases the amount of calcium, thus the calcium levels must be supplemented in order to prevent their deficit. In addition to that slightly diminished levels of calcitriol can be observed in the early stages of CRF, thus it is logical to provide this hormone. However, administering calcitriol may induce hypercalcemia and hyperphosphatemia, which in turn risks the onset of cardiovascular calcifications and complications. Therefore, the calcitriol dosage should be small and then adjusted according to the degree of SH. Neither the PTH levels nor alterations in the phospho-calcium metabolism follow a linear increase appropriate to the decrease in renal function, therefore we propose a treatment strategy which adapts to the different degrees of renal failure.