Comparison of C-terminal and N-terminal PTH in secondary hyperparathyroidism in renal failure.

In 89 patients with disorders in calcium regulation either C-terminal or N-terminal PTH or both, were elevated. In haemodialysis patients the results of C-terminal and N-terminal PTH measurements showed the same trend in 10 patients; in 30 patients only C-terminal and in four patients only N-terminal PTH was elevated. In patients with renal failure, creatinine clearance less than 30 ml/min, both C-terminal and N-terminal PTH were elevated in five patients, C-terminal PTH in 12 patients and N-terminal PTH in none of the patients studied. Fourteen patients with primary hyperparathyroidism were studied; in ten both C-terminal and N-terminal PTH were elevated, in two only C-terminal PTH and in another two only N-terminal PTH was elevated. The results show that there seems to be a better clinical correlation for hyperparathyroidism, in haemodialysis patients and patients with renal failure, using N-terminal PTH determinations rather than C-terminal PTH determinations, because in haemodialysis patients and patients with renal failure split products of the C-terminal region of PTH give unrealistically high PTH results.