Calcium-Corrected Intact PTH: A Clinically Useful Parameter for Quantifying Parathyroid Function in Patients Undergoing Hemodialysis

摘要

Background/Aims: Serum parathyroid hormone (PTH) concentration provides a rough index of the severity of secondary hyperparathyroidism (SHPT) due to chronic renal failure. Since serum PTH inversely related to calcium (Ca) level, we attempted to create a new index based on the relationship. Methods: Our subjects were 70 patients undergoing maintenance hemodialysis (HD) in a single facility. Using multiple pairs of serum Ca corrected for albumin (cCa) and intact PTH (iPTH) values drawn simultaneously, we determined the steepest slope of cCa-iPTH relationship for each individual patient to get a line closely resembling the cCa-PTH sigmoi-dal curve. Results: Based on the slopes, the following equation was obtained: iPTH2 = iPTH1 +(cCa1 -cCa2) X (43 + 0.47 x iPTH1), where the PTH values at any 2 arbitrary values of cCal and cCa2 were assumed to be iPTH1 and iPTH2, respectively. When 'corrected PTH' is defined as the predicted value of iPTH at cCa = 9.0 mg/dl, its correlation was better than iPTH with the total volume of the parathyroid glands estimated by ultrasonography. Similar results were found in 30 parathyroidectomized patients at other facilities. Conclusion: 'Corrected PTH' may represent a useful parameter for assessing the severity of SHPT from single determinations of cCa and iPTH drawn at the same time.