Normalization of reversed bio-intact-PTH(1-84)/intact-PTH ratio after parathyroidectomy in a patient with severe secondary hyperparathyroidism.
The conventional intact-PTH assay detects both (1-84)-PTH and C-terminal fragments. The newer PTH assays, bio-intact-PTH assay and whole-PTH assay, use an antibody that binds only if the first amino acid is present, making it specific for the complete molecule, (1-84)-PTH. Thus, the intact-PTH concentrations are theoretically higher than bio-intact-PTH concentrations, and the ratio of bio-intact-PTH/intact-PTH is usually less than 1. These findings are observed in normal subjects and patients with primary and secondary hyperparathyroidism. Here we present a hemodialysis patient with severe secondary hyperparathyroidism who was found to have abnormally higher plasma bio-intact-PTH concentrations than intact-PTH concentrations, and the abnormally high biointact-PTH/intact-PTH ratio improved after parathyroidectomy (PTx). The patient was a 67-year-old man on maintenance hemodialysis since 1995. Since 2003, he was found to have high plasma intact-PTH concentrations and two swollen parathyroid glands in the neck. PTx with forearm autograft was performed in October 2003. Before PTx, an abnormally high ratio of bio-intact-PTH/intact-PTH was detected (840 pg/ml/770 pg/ml, > 1), while the same ratio was improved to normal range (100 pg/ml/200 pg/ml, < 1). Recently, a few patients with parathyroid carcinoma have been found to have higher (1-84)-PTH concentrations than intact-PTH concentrations with abnormally high (1-84)-PTH/intact-PTH ratio. Moreover, a new molecular form of PTH distinct from (1-84)-PTH was detected in these patients. We speculate that the resected parathyroid gland in our patient might have produced a new molecular form of PTH that was less well detected by the conventional intact-PTH assay.
Tanaka
M
M
Department of Nephrology, Akebono Clinic, Kumamoto, Japan. tanaka@matusita-kai.or.jp
Itoh
K
K
Matsushita
K
K
Matsushita
K
K
Fujii
H
H
Fukagawa
M
M
D000368:Aged; D003940:Diagnostic Techniques, Endocrine; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000097:blood* / Q000601:surgery*; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood*; D016105:Parathyroidectomy
D010281:Parathyroid Hormone