INTACT PARATHYROID-HORMONE LEVELS IN RENAL-INSUFFICIENCY

To define the onset of the rise in intact parathyroid hormone (PTH) le vels in renal insufficiency, we conducted a cross-sectional study of p arameters of mineral metabolism in patients with varying degrees of re nal impairment. Using an immunoradiometric assay to measure intact PTH levels, we found elevations in intact PTH levels as creatinine cleara nce approaches 60 ml/minute (serum creatinine near 1.8) and a signific ant inverse relationship between indices of renal function and intact PTH levels (r = -0.60, P < 0.001 for intact PTH and creatinine clearan ce). Calcium and phosphate revels correlate less strongly with the deg ree of hyperparathyroidism (r = -0.39, P < 0.001 for total calcium; r = 0.31, P < 0.05 for phosphate). As a group, only patients with severe renal failure (creatinine clearance <20 ml/minute) had 1,25-dihydroxy vitamin D levels below normal (11.+/-4 [SEM] pg/dl, normal range 15-60 ). Intact and n-terminal PTH measurements correlate well in this patie nt population with varying degrees of renal insufficiency (r = 0.9, P < 0.001). Intact PTH can be elevated in patients with mild to moderate renal insufficiency, thus efforts to prevent the development of secon dary hyperparathyroidism in renal failure should be undertaken early i n the course of renal insufficiency.