title: Improved insulin sensitivity, preserved beta cell function and improved whole-body glucose metabolism after low-dose growth hormone replacement therapy in adults with severe growth hormone deficiency: a pilot study.
abstract: OBJECTIVE
  Growth hormone-deficient patients show deterioration of insulin sensitivity and beta cell function. High-dose growth hormone treatment often induces further impairment of insulin sensitivity, leading to an increase in insulin and glucose levels or even, in cases of preexisting beta cell defect, to overt diabetes. However, low-dose treatment may improve insulin sensitivity, although data in humans with detailed metabolic phenotyping are as yet not available. We postulated that long-term low-dose growth hormone replacement, restoring IGF-1 to the low-normal range, might beneficially affect glucose metabolism.
  
  
  METHODS
  We studied prospectively the metabolic responses to 24 and 48 weeks of growth hormone treatment in a small group of six adults with severe growth hormone deficiency (four men, two women; age 40-59 years; BMI 30.2 +/- 1 kg/m(2); mean growth hormone dose 0.3 +/- 0.04 mg/day). All participants underwent an oral glucose tolerance test, euglycaemic-hyperinsulinaemic clamp and hyperglycaemic-hyperinsulinaemic clamp plus i.v. L: -arginine on three occasions. Insulin sensitivity was measured by calculating the M value during the steady state of the euglycaemic-hyperinsulinaemic clamp. Insulin secretion and clearance were estimated from AUC(C-peptide), AUC(insulin) and their ratio at each phase of the hyperglycaemic-hyperinsulinaemic clamp.
  
  
  RESULTS
  Growth hormone significantly improved insulin sensitivity (M value 13.8 +/- 2.6 [baseline] vs 19.6 +/- 2.6 [24 weeks] and 23.7 +/- 1.9 [48 weeks] micromol kg(-1) min(-1); p < 0.01). Although the insulin response to glucose and arginine decreased slightly, the disposition index, integrating insulin sensitivity and secretion, significantly increased (p < 0.01), indicating an improvement in whole-body glucose metabolism. Insulin clearance was not affected during treatment (p > 0.05).
  
  
  CONCLUSIONS
  Our data indicate that long-term low-dose growth hormone treatment may improve insulin sensitivity and whole-body glucose metabolism in adults with severe growth hormone-deficiency.
authors.affiliation: Department of Endocrinology, Diabetes and Nutrition, Charité-University Medicine Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12200, Berlin, Germany. ayman.arafat@charite.de
authors.forename: A M
authors.initials: AM
authors.lastname: Arafat
authors.forename: M
authors.initials: M
authors.lastname: Möhlig
authors.forename: M O
authors.initials: MO
authors.lastname: Weickert
authors.forename: C
authors.initials: C
authors.lastname: Schöfl
authors.forename: J
authors.initials: J
authors.lastname: Spranger
authors.forename: A F H
authors.initials: AF
authors.lastname: Pfeiffer
mesh_terms: D000328:Adult; D002096:C-Peptide / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D020249:Hormone Replacement Therapy; D019382:Human Growth Hormone / Q000172:deficiency / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000502:physiology*; D008297:Male; D008875:Middle Aged
chemical_list: D002096:C-Peptide; D007328:Insulin; D019382:Human Growth Hormone; D005947:Glucose