Diagnostic utility of the glucagon stimulation test in comparison to the insulin tolerance test in patients following pituitary surgery

TY - JOUR

T1 - Diagnostic utility of the glucagon stimulation test in comparison to the insulin tolerance test in patients following pituitary surgery

AU - Berg, Christian

AU - Meinel, Timo

AU - Lahner, Harald

AU - Yuece, Ali

AU - Mann, Klaus

AU - Petersenn, Stephan

N1 - Keywords: Adenoma; Adrenal Insufficiency; Adult; Analysis of Variance; Blood Glucose; Chemiluminescent Measurements; Craniopharyngioma; Female; Glucagon; Human Growth Hormone; Humans; Hydrocortisone; Hypopituitarism; Hypothalamo-Hypophyseal System; Insulin; Male; Meningeal Neoplasms; Meningioma; Middle Aged; Neurosurgical Procedures; Pituitary Gland; Pituitary Neoplasms; Pituitary-Adrenal System; Prospective Studies; ROC Curve; Sensitivity and Specificity; Statistics, Nonparametric; Time Factors

PY - 2009

Y1 - 2009

N2 - OBJECTIVE: The glucagon stimulation test (GST) like the insulin tolerance test (ITT) stimulates both ACTH and GH secretion. However, there are limited data with modern assays on sensitivity and specificity for GST in comparison to ITT. The aim of this study was to evaluate the diagnostic utility of the GST for GH deficiency (GHD) and adrenal insufficiency (AI) in patients following pituitary surgery. DESIGN AND PATIENTS: ITT and GST were performed within 7 days in 49 patients at least 3 months after transsphenoidal surgery. Serum GH and cortisol were measured by Immulite 2000 assay (Siemens AG). Receiver-operating characteristic (ROC) analysis was performed to identify the thresholds for GST. RESULTS: In ITT, 18/49 cases were classified as AI. ROC analysis revealed a peak cortisol value >599 nmol/l in GST for adrenal sufficiency with 100% specificity and 32% sensitivity, and a peak cortisol <277 nmol/l with >95% specificity and 72% sensitivity for AI. Of the 49 subjects, 25 (51%) demonstrated levels between these cut-offs and could not be diagnosed by GST alone with sufficient accuracy. Regarding GHD, 21/49 cases were classified as insufficient by ITT. ROC analysis revealed a cut-off of 2.5 ng/ml with 95% sensitivity and 79% specificity. Of the 49 cases, seven (14%) were discordant in terms of defining GHD, with six subjects being treated for GHD according to GST although being sufficient in ITT. CONCLUSION: In our prospective series of patients with pituitary disease, GST is a potential alternative test for the assessment of GH reserve, but is a poor test for ACTH reserve. Test-specific cut-offs should be applied to avoid misinterpretation.

AB - OBJECTIVE: The glucagon stimulation test (GST) like the insulin tolerance test (ITT) stimulates both ACTH and GH secretion. However, there are limited data with modern assays on sensitivity and specificity for GST in comparison to ITT. The aim of this study was to evaluate the diagnostic utility of the GST for GH deficiency (GHD) and adrenal insufficiency (AI) in patients following pituitary surgery. DESIGN AND PATIENTS: ITT and GST were performed within 7 days in 49 patients at least 3 months after transsphenoidal surgery. Serum GH and cortisol were measured by Immulite 2000 assay (Siemens AG). Receiver-operating characteristic (ROC) analysis was performed to identify the thresholds for GST. RESULTS: In ITT, 18/49 cases were classified as AI. ROC analysis revealed a peak cortisol value >599 nmol/l in GST for adrenal sufficiency with 100% specificity and 32% sensitivity, and a peak cortisol <277 nmol/l with >95% specificity and 72% sensitivity for AI. Of the 49 subjects, 25 (51%) demonstrated levels between these cut-offs and could not be diagnosed by GST alone with sufficient accuracy. Regarding GHD, 21/49 cases were classified as insufficient by ITT. ROC analysis revealed a cut-off of 2.5 ng/ml with 95% sensitivity and 79% specificity. Of the 49 cases, seven (14%) were discordant in terms of defining GHD, with six subjects being treated for GHD according to GST although being sufficient in ITT. CONCLUSION: In our prospective series of patients with pituitary disease, GST is a potential alternative test for the assessment of GH reserve, but is a poor test for ACTH reserve. Test-specific cut-offs should be applied to avoid misinterpretation.

U2 - 10.1530/EJE-09-0824

DO - 10.1530/EJE-09-0824

M3 - Journal article

C2 - 19996199

SN - 0804-4643

VL - 162

SP - 477

EP - 482

JO - European Journal of Endocrinology

JF - European Journal of Endocrinology

IS - 3

ER -