title: In vitro parathyroid hormone release in patients with secondary hyperparathyroidism.
abstract: BACKGROUND
  The purpose of this study was to determine the precise endocrine characteristics of parathyroid function in secondary hyperparathyroidism (sHPT).
  
  
  METHODS
  We examined the effects of extracellular ionized calcium (Ca2+) varying from 0.5 to 2.0 mM on parathyroid hormone (PTH) release in parathyroid cell suspensions using a mid-regional PTH assay. Cells were obtained from 26 patients with sHPT who were divided into two groups according to the type of hyperplasia they exhibited, either nodular (n = 16) or diffuse (n = 10). For comparison, we also analyzed data from nine patients with primary hyperparathyroidism (pHPT; adenomas).
  
  
  RESULTS
  Significant in vitro suppression of PTH release by Ca2+ was observed in the majority of subjects, regardless of the histologic abnormality. The pHPT group exhibited no significant relationship between clinical and in vitro data. In contrast, in the sHPT group (taken as a whole), suppression of PTH release by Ca2+ exhibited a plateau at a total serum calcium concentration of 2.5 mmol/L, and a parathyroid gland weight of 2 g.
  
  
  CONCLUSIONS
  These findings suggest that there is a curvilinear relationship in sHPT, but not pHPT, between the in vitro calcium sensitivity of parathyroid cells and total serum calcium, as well as gland weight. The in vitro calcium sensitivity in sHPT remains constant when the total serum calcium concentration exceeds 2.5 mmol/L, or when the gland weight exceeds 2 g.
authors.affiliation: Department of Urology, Oita Medical University, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Yano
authors.forename: Y
authors.initials: Y
authors.lastname: Nomura
authors.forename: H
authors.initials: H
authors.lastname: Mizoguchi
authors.forename: J
authors.initials: J
authors.lastname: Ogata
mesh_terms: D000236:Adenoma / Q000150:complications; D000328:Adult; D000368:Aged; D015415:Biomarkers; D002118:Calcium / Q000097:blood / Q000494:pharmacology* / Q000502:physiology; D002470:Cell Survival; D005260:Female; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000378:metabolism* / Q000473:pathology; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D010280:Parathyroid Glands / Q000473:pathology; D010281:Parathyroid Hormone / Q000378:metabolism*; D010282:Parathyroid Neoplasms / Q000150:complications
chemical_list: D015415:Biomarkers; D010281:Parathyroid Hormone; D002118:Calcium