title: Proinsulin serum concentrations in women with polycystic ovary syndrome: a marker of beta-cell dysfunction?
abstract: BACKGROUND
  The aim of this study was to establish the effect of polycystic ovary syndrome (PCOS) adjusted for adiposity on proinsulin concentrations.
  
  
  METHODS
  Ninety-one women with PCOS and 72 normal cycling (NC) women were recruited. A 2 h, 75 g oral glucose tolerance test was performed. Glucose and insulin were measured in each sample. Proinsulin and C-peptide were determined at 0 and 30 min and the fasting proinsulin/insulin ratio (PI/I) was calculated. Insulin sensitivity was estimated by insulin sensitivity index (ISI) composite, and beta-cell function was estimated by insulinogenic index.
  
  
  RESULTS
  Insulin, proinsulin and C-peptide concentrations were higher in women with PCOS than in NC women (P < 0.05). PI/I and insulinogenic index were similar in both groups. Proinsulin concentrations increased with body mass index (P < 0.05) only in women with PCOS; therefore, proinsulin concentrations were higher in obese PCOS patients compared with obese control women (P < 0.05). Moreover, a positive association between proinsulin concentrations and waist diameter adjusted for C-peptide (P < 0.05) and a negative association between proinsulin concentrations and ISI composite values were observed in PCOS patients (P < 0.05).
  
  
  CONCLUSIONS
  Data suggest that in PCOS patients an elevated proinsulin concentration could reflect insulin resistance more than beta-cell dysfunction. However, the elevated concentration of proinsulin in these patients could also result from impaired beta-cell function resulting from intra-abdominal obesity independently of insulin resistance.
authors.affiliation: Department of Medicine, San Juan de Dios Hospital, School of Medicine, University of Chile, Santiago, Chile.
authors.forename: M
authors.initials: M
authors.lastname: Maliqueo
authors.forename: I
authors.initials: I
authors.lastname: Atwater
authors.forename: R
authors.initials: R
authors.lastname: Lahsen
authors.forename: F
authors.initials: F
authors.lastname: Pérez-Bravo
authors.forename: B
authors.initials: B
authors.lastname: Angel
authors.forename: T
authors.initials: T
authors.lastname: Sir-Petermann
mesh_terms: D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D001824:Body Constitution; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood; D005215:Fasting; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D007515:Islets of Langerhans / Q000503:physiopathology*; D009765:Obesity / Q000150:complications / Q000503:physiopathology; D011085:Polycystic Ovary Syndrome / Q000097:blood* / Q000150:complications / Q000503:physiopathology; D011384:Proinsulin / Q000097:blood*
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D011384:Proinsulin