title: Can a glucagon stimulation test characterized by lower GH cut-off value be used for the diagnosis of growth hormone deficiency in adults?
abstract: OBJECTIVE
  The aim of this study was to assess diagnostic values of insulin tolerance test (ITT), glucagon stimulation test (GST), and insulin like growth factor-I (IGF-I) level, to find optimal GH cut-off values for GST, and to evaluate efficiencies of patient age, gender, body-mass index (BMI), and additional pituitary hormone deficiencies (PHDs) in the diagnosis of growth hormone deficiency (GHD).
  
  
  METHODS
  This retrospective study involved 216 patients with a pituitary disease and 26 healthy controls. Age, gender, BMI, medical histories, and hormonal data including baseline and stimulated hormone values were evaluated. Three cut-off values for peak GH responses to stimulation tests were evaluated: (a) 3.00 µg/L on ITT, (b) 3.00 µg/L on GST, and (c) 1.07 µg/L on GST.
  
  
  RESULTS
  According to the ITT, GST with 3.00 µg/L cut-off, and GST with 1.07 µg/L cut-off, GHD was present in 86.1, 74.5, and 54.2 % patients, respectively. Patient age, BMI, and number of PHDs, but not gender, were found to be correlated with IGF-I and peak GH concentrations. All patients with an IGF-I concentration ≤95 ng/ml or ≥3 PHD had GHD. None of the patients with adequate GH response to the GST with 1.07 µg/L cut-off, but blunted responses to ITT and GST with 3.00 µg/L cut-off, had ≥3 PHDs. 12 out of 26 (46.2 %) healthy subjects failed the GST with 3.00 µg/L cut-off, but not with 1.07 µg/L cut-off.
  
  
  CONCLUSIONS
  Patient age, IGF-I, BMI, and number of PHDs are efficient factors associated with the diagnosis of GHD. A 4 h GST with a diagnostic GH threshold of 1.07 µg/L seems to be a good diagnostic method for GHD.
authors.affiliation: Department of Endocrinology, Erciyes University Medical School, 38039, Kayseri, Turkey.
authors.forename: Halit
authors.initials: H
authors.lastname: Diri
authors.affiliation: Department of Endocrinology, Erciyes University Medical School, 38039, Kayseri, Turkey.
authors.forename: Zuleyha
authors.initials: Z
authors.lastname: Karaca
authors.affiliation: Department of Endocrinology, Erciyes University Medical School, 38039, Kayseri, Turkey.
authors.forename: Yasin
authors.initials: Y
authors.lastname: Simsek
authors.affiliation: Department of Endocrinology, Erciyes University Medical School, 38039, Kayseri, Turkey.
authors.forename: Fatih
authors.initials: F
authors.lastname: Tanriverdi
authors.affiliation: Department of Endocrinology, Erciyes University Medical School, 38039, Kayseri, Turkey.
authors.forename: Kursad
authors.initials: K
authors.lastname: Unluhizarci
authors.affiliation: Department of Neurosurgery, Erciyes University Medical School, Kayseri, Turkey.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Selcuklu
authors.affiliation: Department of Endocrinology, Erciyes University Medical School, 38039, Kayseri, Turkey. fktimur@erciyes.edu.tr.
authors.forename: Fahrettin
authors.initials: F
authors.lastname: Kelestimur
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005934:Glucagon / Q000097:blood; D019382:Human Growth Hormone / Q000172:deficiency*; D006801:Humans; D007018:Hypopituitarism / Q000097:blood* / Q000175:diagnosis*; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D007328:Insulin; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D005934:Glucagon
keywords: Glucagon stimulation test; Growth hormone deficiency; IGF-I; Insulin tolerance test