title: Assessment of biochemical control of acromegaly during treatment with somatostatin analogues by oral glucose load and insulin-like growth factor I.
abstract: BACKGROUND
  The use of oral glucose tolerance test (OGTT) in evaluating biochemical control in acromegalic patients on somatostatin analogues (SSA) has recently been questioned.
  
  
  OBJECTIVE
  To gain further insights into this topic, we analyzed basal and nadir GH levels during OGTT in acromegalic patients on SSA.
  
  
  METHODS
  Basal IGF-I and GH values, as well as GH levels along the test, were analyzed in 115 standard OGTT performed in 33 acromegalic patients followed up between 1993 and 2009. All patients were on SSA at the time of the study; 22 of them had previously undergone unsuccessful surgery. No patient had undergone radiotherapy. GH suppression was considered normal when the hormonal value fell to <1 μg/l during OGTT. Diagnostic accuracy was analyzed by receiver operating characteristic (ROC) curves.
  
  
  RESULTS
  ROC analysis showed that the GH basal value yielding the best specificity (100%) was 3.9 μg/l. All patients with basal GH>3.9 μg/l displayed lack of GH suppression after OGTT and 80% also displayed high IGF-I. Conversely, patients with basal GH<3.9 μg/l presented a variable biochemical pattern with half of them failing to suppress GH after OGTT and 36.6% displaying high IGF-I levels.
  
  
  CONCLUSIONS
  Our results show that baseline GH levels >3.9 μg/l are predictive of absent OGTT-dependent GH suppression; however, 20% of these patients display partial biochemical control (normal IGF-I levels). On the other hand, basal GH values <3.9 μg/l are not predictive of GH suppressibility by glucose and are often discordant with IGF-I levels.
authors.affiliation: University of Milan, Milan, Italy. massimo.scacchi@unimi.it
authors.forename: M
authors.initials: M
authors.lastname: Scacchi
authors.forename: C
authors.initials: C
authors.lastname: Carzaniga
authors.forename: G
authors.initials: G
authors.lastname: Vitale
authors.forename: L M
authors.initials: LM
authors.lastname: Fatti
authors.forename: F
authors.initials: F
authors.lastname: Pecori Giraldi
authors.forename: M
authors.initials: M
authors.lastname: Andrioli
authors.forename: A
authors.initials: A
authors.lastname: Cattaneo
authors.forename: F
authors.initials: F
authors.lastname: Cavagnini
mesh_terms: D000172:Acromegaly / Q000188:drug therapy* / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018491:Dopamine Agonists / Q000627:therapeutic use; D005260:Female; D005951:Glucose Tolerance Test; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000627:therapeutic use*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D018491:Dopamine Agonists; D019382:Human Growth Hormone; D013004:Somatostatin; D007334:Insulin-Like Growth Factor I