title: Hyperinsulinemia and urinary calcium excretion in calcium stone formers with idiopathic hypercalciuria.
abstract: BACKGROUND
  Calcium stone formers with idiopathic hypercalciuria (IH) are known to exhibit an exaggerated postprandial rise in urine calcium excretion compared with non-stone-forming individuals, and insulin has been proposed to mediate this difference.
  
  
  OBJECTIVE
  Our objective was to investigate the impact of hyperinsulinemia on urine calcium excretion in IH compared with non-stone-forming controls.
  
  
  METHODS
  Ten IH patients and 22 control non-stone-forming subjects (8 lean and 14 overweight and obese) participated at the University of Texas Southwestern Clinical and Translational Research Center.
  
  
  METHODS
  After stabilization on a fixed metabolic diet, subjects underwent a hyperinsulinemic-euglycemic clamp. Fasting 2-hour urine specimens were collected before and during the clamp.
  
  
  METHODS
  Changes in fractional calcium excretion (F(E)Ca) during the clamp were compared between the 3 groups of subjects (IH, overweight/obese controls, and lean controls). Insulin sensitivity was measured by glucose disposal rate.
  
  
  RESULTS
  IH had significantly higher 24-hour urine calcium excretion than controls, and exhibited similar age, body mass index, and insulin sensitivity as overweight/obese controls. The hyperinsulinemic-euglycemic clamp resulted in a significant increase in serum insulin with no significant changes in serum calcium and glucose. This was accompanied by a small increase in F(E)Ca, with no significant differences between the 3 groups. There was no correlation between insulin sensitivity and 24-hour urine calcium or the change in F(E)Ca during the hyperinsulinemic clamp.
  
  
  CONCLUSIONS
  The rise in urine calcium associated with euglycemic hyperinsulinemia was small and not statistically different between IH and non-stone-forming controls. Insulin is therefore unlikely to play a significant pathogenetic role in IH.
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
authors.forename: Vivienne
authors.initials: V
authors.lastname: Yoon
authors.forename: Beverley
authors.initials: B
authors.lastname: Adams-Huet
authors.forename: Khashayar
authors.initials: K
authors.lastname: Sakhaee
authors.forename: Naim M
authors.initials: NM
authors.lastname: Maalouf
mesh_terms: D000328:Adult; D002118:Calcium / Q000652:urine*; D005260:Female; D006801:Humans; D053565:Hypercalciuria / Q000209:etiology / Q000652:urine*; D006946:Hyperinsulinism / Q000652:urine*; D007669:Kidney Calculi / Q000652:urine*; D008297:Male; D008875:Middle Aged
chemical_list: D002118:Calcium
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