title: The relationship between serum calcium level and early-phase insulin secretion in normoglycemic and pre-diabetic individuals.
abstract: BACKGROUND
  Type 2 diabetes mellitus (T2DM) is linked to altered calcium metabolism. However, little is known about the relationship between serum calcium levels and early-phase insulin secretion in subjects with normoglycemic tolerance (NGT) or prediabetes (preDM).
  
  
  METHODS
  In this gender-separated cross-sectional study, 352 subjects with NGT (215 men and 137 women; age: 48.8±9.1 years and 51.6±6.7 years, respectively) and 316 subjects with preDM (231 men and 85 women; age: 52.5±8.6 years and 54.2±8.0 years, respectively) were examined. Following a 75-g oral glucose tolerance test, early-phase insulin secretion was estimated using the insulinogenic index (IGI) [ΔInsulin(30-0 min)/ΔGlucose(30-0 min)].
  
  
  RESULTS
  Simple linear regression analysis showed that IGI was positively correlated with serum calcium and albumin-adjusted calcium levels in men with NGT and preDM. However, IGI was not correlated with calcium levels in women with NGT and preDM. Multivariate linear regression analysis of men with NGT revealed that the albumin-adjusted calcium level was the major predictor of IGI, responsible for 5.1% of its variation (P=0.003). In addition, in men with preDM, the albumin-adjusted calcium level was one of the predictors of IGI, responsible for 3.8% of its variation (P=0.004). These associations were independent of age, BMI, and HbA1c.
  
  
  CONCLUSIONS
  In non-diabetic Japanese men, serum calcium levels significantly correlate with early-phase insulin secretion. Serum calcium levels may be an independent predictor of β-cell function in men.
authors.affiliation: Department of Internal Medicine, Iida Municipal Hospital, Nagano, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Shimodaira
authors.affiliation: Department of Internal Medicine, Iida Municipal Hospital, Nagano, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Niwa
authors.affiliation: Department of Internal Medicine, Iida Municipal Hospital, Nagano, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakajima
authors.affiliation: Department of Internal Medicine, Iida Municipal Hospital, Nagano, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Department of Internal Medicine, Iida Municipal Hospital, Nagano, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Hanyu
authors.affiliation: Department of Pathology and Microbiology, Division of Laboratory Medicine, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nakayama
mesh_terms: D000328:Adult; D002118:Calcium / Q000097:blood*; D005260:Female; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000097:blood*; D012737:Sex Factors
chemical_list: D007328:Insulin; D002118:Calcium