Revised GH and cortisol cut-points for the glucagon stimulation test in the evaluation of GH and hypothalamic–pituitary–adrenal axes in adults: results from a prospective randomized multicenter study

Amir H. Hamrahian, Kevin C.J. Yuen, Murray B. Gordon, Karen J. Pulaski-Liebert, James Bena, Beverly M.K. Biller

Research output: Contribution to journalArticlepeer-review

Abstract

Context: Recent studies suggest using lower GH cut-points for the glucagon stimulation test (GST) in diagnosing adult GH deficiency (GHD), especially in obese patients. There are limited data on evaluating GH and hypothalamic–pituitary–adrenal (HPA) axes using weight-based dosing for the GST. Objective: To define GH and cortisol cut-points to diagnose adult GHD and secondary adrenal insufficiency (SAI) using the GST, and to compare fixed-dose (FD: 1 or 1.5 mg in patients >90 kg) with weight-based dosing (WB: 0.03 mg/kg). Response to the insulin tolerance test (ITT) was considered the gold standard, using GH and cortisol cut-points of ≥3 ng/ml and ≥18 µg/dL, respectively. Design: 28 Patients with hypothalamic-pituitary disease and 1–2 (n = 14) or ≥3 (n = 14) pituitary hormone deficiencies, and 14 control subjects matched for age, sex, estrogen status and body mass index (BMI) underwent the ITT, FD- and WB-GST in random order. Results: Age, sex ratio and BMI were comparable between the three groups. The best GH cut-point for diagnosis of GHD was 1.0 (92 % sensitivity, 100 % specificity) and 2.0 ng/mL (96 % sensitivity and 100 % specificity) for FD- and WB-GST, respectively. Age negatively correlated with peak GH during FD-GST (r = −0.32, P = 0.04), but not WB-GST. The best cortisol cut-point for diagnosis of SAI was 8.8 µg/dL (92 % sensitivity, 100 % specificity) and 11.2 µg/dL (92 % sensitivity and 100 % specificity) for FD-GST and WB-GST, respectively. Nausea was the most common side effect, and one patient had a seizure during the FD-GST. Conclusion: The GST correctly classified GHD using GH cut-points of 1 ng/ml for FD-GST and 2 ng/ml for WB-GST, hence using 3 ng/ml as the GH cut-point will misclassify some GH-sufficient adults. The GST may also be an acceptable alternative to the ITT for evaluating the HPA axis utilizing cortisol cut-points of 9 µg/dL for FD-GST and 11 µg/dL for WB-GST.

Original languageEnglish (US)
Pages (from-to)332-341
Number of pages10
JournalPituitary
Volume19
Issue number3
DOIs
StatePublished - Jun 1 2016
Externally publishedYes

Keywords

  • Adrenal insufficiency
  • Adult growth hormone deficiency
  • Diagnosis
  • Glucagon stimulation test
  • Weight based

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology

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