THE ROLE OF PHOSPHORUS RESTRICTION IN PRE VENTING AND CORRECTING SECONDARY HYPERPARATHYROIDISM IN UREMIC ADULTS

Secondary hyperparathyroidism (HPT II) occurs early in the course of c hronic renal failure (CRF), mainly because of decreased calcitriol lev els, low levels of serum calcium, retention of phosphorus, abnormal pa rathyroid gland function and hyperplasia, and peripheral resistance to the action of parathormone (PTH). Amongst these factors, phosphorus r etention plays a crucial role in moderate and advanced CRF, by inhibit ing renal calcitriol synthesis, lowering serum calcium levels and stim ulating PTH secretion. In patients with mild CRF, phosphorus restricti on prevents the development of HPT II by increasing renal calcitriol s ecretion. In patients with advanced CRF, the suppressive effect of pho sphorus restriction may be obtained independent of any changes in plas ma calcitriol levels, suggesting a direct effect of phosphorus on para thyroid function. Phosphorus restriction should be used in the early s tages of CRF, together with a sufficient intake of calcium in the form of phosphorus chelating salts. When phosphorus and calcium serum conc entrations are normalised but PTH levels are not in the target range, 1 alpha hydroxy vitamin D3 derivatives may be used, with a careful mon itoring to avoid high serum levels of phosphorus or calcium.