title: Age changes the diagnostic accuracy of mean profile and nadir growth hormone levels after oral glucose in postoperative patients with acromegaly.
abstract: BACKGROUND
  This analytical, retrospective study was designed to select cut-off thresholds of mean GH levels during a diurnal profile and nadir GH levels after oral glucose tolerance test (OGTT) according to age to diagnose surgical remission of acromegaly.
  
  
  METHODS
  One hundred forty-one patients (76 women, aged 44 +/- 15 years and 65 men, aged 43 +/- 13 years) were included in this study. For the purpose of this study, remission was based on insulin-like growth factor-I (IGF-I) levels in the normal range for age. Diagnostic accuracy was analysed by receiving-operator characteristics (ROC) curves in the entire series, and in young (20-40 years), middle-aged (41-60 years) and older patients (> 60 years), separately.
  
  
  RESULTS
  Sixty patients (42.6%) had normal IGF-I levels after surgery. In the entire series, in young and in middle-aged patients, the ROC analysis showed that optimum cut-off for mean GH levels was 2.3 microg/l (diagnostic accuracy range, 94-97%) whereas that for nadir GH after OGTT were, respectively, 0.85, 0.9 and 0.8 microg/l (diagnostic accuracy range, 90-95%). In the older patients, the optimum cut-off selected for mean GH levels was 1.4 microg/l and that for nadir GH after OGTT was 0.5 microg/l (diagnostic accuracy, 100% for both). The comparative analysis of the ROC curves did not show any significant difference between mean GH and nadir GH after OGTT (P = 0.21).
  
  
  CONCLUSIONS
  The criteria currently accepted for diagnosing post-surgical remission of acromegaly have high diagnostic accuracy only in the patients aged below 60 years. In older patients, lower cut-offs (i.e. = 1.4 microg/l for fasting GH and = 0.5 microg/l for nadir GH after OGTT) predict normal IGF-I levels. Mean GH levels during a diurnal profile have similar diagnostic accuracy of nadir GH levels after OGTT. This suggests that OGTT is not necessary to establish surgical cure.
authors.affiliation: Department of Molecular and Clinical Endocrinology and Oncology, Section of Endocrinology, University Federico II of Naples, Naples, Italy. colao@unina.it
authors.forename: Annamaria
authors.initials: A
authors.lastname: Colao
authors.forename: Rosario
authors.initials: R
authors.lastname: Pivonello
authors.forename: Luigi M
authors.initials: LM
authors.lastname: Cavallo
authors.forename: Maria
authors.initials: M
authors.lastname: Gaccione
authors.forename: Renata S
authors.initials: RS
authors.lastname: Auriemma
authors.forename: Felice
authors.initials: F
authors.lastname: Esposito
authors.forename: Paolo
authors.initials: P
authors.lastname: Cappabianca
authors.forename: Gaetano
authors.initials: G
authors.lastname: Lombardi
mesh_terms: D000172:Acromegaly / Q000097:blood / Q000175:diagnosis* / Q000601:surgery; D000328:Adult; D000367:Age Factors; D000368:Aged; D005260:Female; D005947:Glucose; D005951:Glucose Tolerance Test; D013006:Growth Hormone / Q000097:blood* / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000378:metabolism / Q000601:surgery; D011184:Postoperative Period; D015175:Prolactinoma / Q000601:surgery; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D016896:Treatment Outcome
chemical_list: D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D005947:Glucose