title: The whole-PTH/intact-PTH ratio is a useful predictor of severity of secondary hyperparathyroidism.
abstract: Background. The newer parathyroid hormone (PTH) assay, whole-PTH, uses an antibody that binds the region harbouring the first amino acid, making it specific for the complete molecule, 1-84-PTH. Especially among dialysis patients, it has been reported that the level of whole-PTH can be calculated as ∼60% of their intact-PTH value. In addition, since 1-84-PTH is part of intact-PTH, the whole-PTH/intact-PTH ratio should not theoretically exceed 1. However, an abnormally high 1-84-PTH/intact-PTH ratio is reported in a few patients with parathyroid carcinoma, primary hyperparathyroidism and secondary hyperparathyroidism. In this study, we examined the correlation between the 1-84-PTH/intact-PTH ratio and the severity of hyperparathyroidism in patients on haemodialysis (HD). Patients and methods. The study population comprised 196 HD patients (males 113, females 83, age 67.4 ± 13.6 years, HD period 8.1 ± 7.3 years; mean ± SD). The whole-PTH/intact-PTH ratio was compared in patients with high PTH levels (intact-PTH ≥300 pg/ ml; high PTH group, n = 32), moderate PTH levels (intact-PTH >150-<300 pg/ml; moderate PTH group, n = 50) and low PTH levels (intact-PTH <150 pg/ml; low PTH group, n = 114). The ratio was also compared in 25 patients with at least one enlarged gland >0.5 cm(3) suggesting nodular hyperplasia, as determined by power Doppler ultrasonography (hyperplasia group) with seven patients without enlarged gland (non-hyperplasia group) and six patients who had undergone total parathyroidectomy (post-PTx group). Results. The whole-PTH/intact-PTH ratio of the high PTH group (0.68 ± 0.1) was significantly higher than those of the moderate (0.61 ± 0.1, P < 0.001) and low (0.52 ± 0.1, P < 0.001) groups. Moreover, the ratio was significantly higher in the hyperplasia group (0.70 ± 0.1) than those in the non-hyperplasia group (0.59 ± 0.1, P < 0.05) and post-PTx group (0.456 ± 0.12, P < 0.001). Conclusions. The whole-PTH/intact-PTH ratio correlated with the severity of hyperparathyroidism. Our results suggest that the ratio might be a useful predictor of severity of secondary hyperparathyroidism in HD patients.
authors.affiliation: Department of Nephrology, Akebono Clinic, Kumamoto.
authors.forename: Motoko
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Division of Nephrology and Kidney Center , Kobe University School of Medicine , Kobe , Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Komaba
authors.affiliation: Department of Nephrology, Akebono Clinic, Kumamoto.
authors.forename: Kazuko
authors.initials: K
authors.lastname: Itoh
authors.affiliation: Department of Nephrology, Akebono Clinic, Kumamoto.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Matsushita
authors.affiliation: Department of Nephrology, Akebono Clinic, Kumamoto.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Matshushita
authors.affiliation: Division of Nephrology and Kidney Center , Kobe University School of Medicine , Kobe , Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hamada
authors.affiliation: Division of Nephrology and Kidney Center , Kobe University School of Medicine , Kobe , Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Fujii
authors.affiliation: Division of Nephrology and Kidney Center , Kobe University School of Medicine , Kobe , Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Fukagawa
keywords: 1–84-PTH; haemodialysis; new molecular form of PTH; secondary hyperparathyroidism; whole-PTH/intact-PTH ratio