[PTH assay: new and future]

Bone disease is one of the main complications in chronic dialysis patients, adynamic bone disease has become a major problem. It has been suggested that higher (parathyroid hormone) PTH is needed to maintain normal bone turnover in uremia. Thus, target PTH level has been recently set at 150 - 200 pg/ml by intact PTH assay. Nevertheless, even the intact PTH assay has several critical problems. Since PTH molecule is unstable, intact PTH assay may not evaluate the actual activity of circulating PTH. On the other hand, due to the recognition site of the antibody, conventional intact PTH assay may detect 7-84 PTH in addition to 1-84 PTH. Furthermore recent data suggest that 7-84 PTH fragments inhibits the action of 1-84 PTH. Thus, conventional intact PTH assay may overestimate the actual activity of circulating PTH molecules in uremic patients. Whole PTH assay, which detects only 1-84 PTH may be a better method for the evaluation of actual PTH activity. Target range of PTH in uremic patients should be set by deliberately considering these problems in near future.