title: PTH inhibition rate is useful in the detection of early-stage primary hyperparathyroidism.
abstract: OBJECTIVE
  This study was to establish biochemical thresholds for the intravenous calcium suppression test in the early diagnosis of primary hyperparathyroidism (PHPT).
  
  
  METHODS
  One hundred and thirty-three patients were divided into three groups: Group 1: surgically proven hypercalcemic PHPT, Group 2 surgically proven mild PHPT, and Group 3: normocalcemia with elevated serum PTH levels. Intravenous calcium suppression tests were performed in Groups 2 and 3 as well as in 20 controls with normal serum calcium and PTH concentrations.
  
  
  RESULTS
  The serum PTH inhibition rate (PTH-IR) was less pronounced in Group 2 compared with Group 3 (P<0.001) and the controls (P<0.001). Receiver operating characteristic curve analysis suggests that a serum calcium level higher than 2.43mmol/L and a PTH-IR less than 73% may differentiate Group 2 from normal controls.
  
  
  CONCLUSIONS
  It is quite useful to combine serum calcium levels with the PTH-IR to identify patients at early stage of PHPT, even in the presence of vitamin D deficiency.
authors.affiliation: Department of Endocrine and Metabolic Diseases, Rui-jin Hospital, Shanghai Jiao-Tong University School of Medicine, 197 Rui-jin Er Road, Shanghai, 200025, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhao
authors.forename: Min-jia
authors.initials: MJ
authors.lastname: Zhang
authors.forename: Hong-yan
authors.initials: HY
authors.lastname: Zhao
authors.forename: Li-hao
authors.initials: LH
authors.lastname: Sun
authors.forename: Jie-li
authors.initials: JL
authors.lastname: Li
authors.forename: Bei
authors.initials: B
authors.lastname: Tao
authors.forename: Wei-qing
authors.initials: WQ
authors.lastname: Wang
authors.forename: Guang
authors.initials: G
authors.lastname: Ning
authors.forename: Jian-min
authors.initials: JM
authors.lastname: Liu
mesh_terms: D000328:Adult; D002118:Calcium / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000097:blood / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010281:Parathyroid Hormone / Q000037:antagonists & inhibitors* / Q000097:blood; D012372:ROC Curve
chemical_list: D010281:Parathyroid Hormone; D002118:Calcium