Parathyroid hormone, a uremic toxin.

Despite the innovations in the treatment of secondary hyperparathyroidism, there are uremic patients with marked elevation in PTH levels. Uremic toxicity is in part attributable to the excess of circulating PTH. It has been known for many years that PTH may induce changes in cell calcium, a key intracellular signal required for normal cell function. The effect of PTH in dialysis patients is not limited to bone; the diversity of biologic effects of PTH is summarized in this review. In addition, the present review addresses other issues: (i) the presence of different circulating PTH fragments in uremic patients, (ii) the PTH assays currently utilized to measure circulating PTH, and (iii) the fact that some of the PTH effects seen in uremic patients may be due to the interaction of C-terminal PTH fragment with putative C-terminal PTH receptors.