title: Rapid suppression of growth hormone concentration by overeating: potential mediation by hyperinsulinemia.
abstract: BACKGROUND
  The very low GH concentration in obesity is commonly attributed to high body fat mass; however, the influence of overeating on GH secretion is not clear.
  
  
  OBJECTIVE
  The aim of the study was to examine the effects of 2 wk of overeating on changes in GH secretion.
  
  
  METHODS
  Subjects were admitted to the hospital and stayed within the Michigan Clinical Research Unit throughout the entire 2-wk overeating period.
  
  
  METHODS
  We studied seven healthy, nonobese men (body mass index, 24 ± 1 kg/m(2); age, 25 ± 1 yr).
  
  
  METHODS
  Subjects ate standardized meals containing 70 kcal/kg fat free mass/d (∼4000 kcal/d) for 2 wk.
  
  
  METHODS
  Twenty-four-hour plasma concentrations of GH (every 20 min) and insulin (every 2 h) were measured before overeating (baseline), on d 3, and after 2 wk of overeating.
  
  
  RESULTS
  Compared with baseline, average 24-h plasma GH concentration declined nearly 80% by d 3 of overeating (1.30 ± 0.18 vs. 0.36 ± 0.09 ng/ml; P = 0.01). This marked suppression of GH secretion occurred in the absence of an increase in body weight (77.0 ± 2.2 vs. 76.4 ± 2.4 kg). At the same time, average 24-h insulin concentration doubled (16.6 ± 2.1 vs. 31.7 ± 5.8 μU/ml; P = 0.009). After 2 wk, body weight significantly increased (79.0 ± 2.1 kg; P < 0.001), and body fat increased by more than 10% (P = 0.002). However, this did not induce a further suppression in plasma GH concentration (0.33 ± 0.08 ng/ml).
  
  
  CONCLUSIONS
  Only a few days of overeating markedly suppressed GH secretion before any measurable weight gain and was accompanied by chronic hyperinsulinemia. Increased body weight and body fat by 2 wk of overeating did not further suppress GH secretion.
authors.affiliation: School of Kinesiology, University of Michigan, 401 Washtenaw Avenue, Ann Arbor, Michigan 48109-2214, USA.
authors.forename: Andrea S
authors.initials: AS
authors.lastname: Cornford
authors.forename: Ariel L
authors.initials: AL
authors.lastname: Barkan
authors.forename: Jeffrey F
authors.initials: JF
authors.lastname: Horowitz
mesh_terms: D050154:Adiposity / Q000502:physiology; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D002940:Circadian Rhythm; D005230:Fatty Acids, Nonesterified / Q000097:blood; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D006946:Hyperinsulinism / Q000097:blood* / Q000209:etiology*; D006963:Hyperphagia / Q000097:blood*; D007328:Insulin / Q000097:blood*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D014280:Triglycerides / Q000097:blood; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D018972:Insulin-Like Growth Factor Binding Protein 3; D014280:Triglycerides; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D006854:Hydrocortisone