title: Comparison of oral glucose tolerance test (OGTT) 100 g with OGTT 75 g for evaluation of acromegalic patients and the impact of gender on test reproducibility.
abstract: BACKGROUND
  Growth hormone (GH) measurements during an oral glucose tolerance test (OGTT) are essential for the diagnosis and follow-up management of acromegaly. However, both 100 g glucose (OGTT(100) ) and 75 g glucose (OGTT(75) ) test variants are in clinical use. Whether the tests are interchangeable concerning GH nadir and test interpretation is unclear. Furthermore, information on test reproducibility and the impact of gender is scarce.
  
  
  OBJECTIVE
  To compare both tests in acromegalic patients and to evaluate test reproducibility with respect to gender.
  
  
  METHODS
  OGTT(100) and OGTT(75) were performed on two consecutive days in 54 acromegalic patients (46·9 ± 1·8 years, 30 women). OGTT(75) was repeated on three different occasions in 11 healthy men and 13 healthy women at different phases of the menstrual cycle.
  
  
  RESULTS
  GH nadirs were comparable between tests [2·40 ± 0·52 (OGTT(100) ) and 2·46 ± 0·54 μg/l (OGTT(75) ); P = 0·356]. There were no differences at any time point in the mean values of GH, serum glucose or insulin between the two test variants. Test interpretation was highly consistent between the OGTT(100) and OGTT(75) [area under the receiver operated curve (ROC) = 0·995]. In men, GH, insulin and glucose measurements during OGTT(75) were highly reproducible. In women, however, basal and GH nadirs were significantly higher midcycle (P < 0·05).
  
  
  CONCLUSIONS
  In acromegalic patients, there is no difference in GH nadirs and test interpretation after the ingestion of 100 g or 75 g glucose. The OGTT(75) is highly reproducible in men, but in women, it should be performed preferably in the early follicular phase.
authors.affiliation: Department of Endocrinology, Diabetes and Nutrition, Charité-University Medicine Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: A M
authors.initials: AM
authors.lastname: Arafat
authors.forename: L
authors.initials: L
authors.lastname: Müller
authors.forename: M
authors.initials: M
authors.lastname: Möhlig
authors.forename: B
authors.initials: B
authors.lastname: Mayr
authors.forename: N
authors.initials: N
authors.lastname: Kremenevskaya
authors.forename: A F H
authors.initials: AF
authors.lastname: Pfeiffer
authors.forename: M
authors.initials: M
authors.lastname: Buchfelder
authors.forename: C
authors.initials: C
authors.lastname: Schöfl
mesh_terms: D000172:Acromegaly / Q000097:blood*; D000328:Adult; D005260:Female; D005951:Glucose Tolerance Test / Q000379:methods*; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012737:Sex Factors
chemical_list: D019382:Human Growth Hormone