Endocrine Abstracts

JOINT2829

Introduction: The insulin tolerance test (ITT) remains the ‘gold standard’ test for assessing growth hormone (GH) deficiency (GHD) in adults. However, this test is labour and resource intensive. Furthermore, ITT causes unpleasant symptoms resulting from the hypoglycaemia which is required to stimulate growth hormone secretion. Due to safety concerns, the use of ITT in the UK has been limited to a few endocrine centres with expertise and confidence in performing this test. Consequently, some patients who likely have GHD are not being offered appropriate and timely assessment and treatment. Macimorelin, a novel orally administered GH-releasing peptide is a safe alternative with diagnostic accuracy comparable to ITT.

Aim: The aim of this audit is to compare the real-life experience of performing ITT compared with macimorelin test (MT) in terms of resource requirements, cost and adverse events reported by each patient who have undergone these tests.

Methodology: This is a retrospective review of 12 ITTs, from January to December 2019, and 12 MTs, from March 2023 to February 2024, performed in a tertiary endocrine centre in Birmingham, UK.

Findings: The average time for completing an ITT was 199 minutes (range= 189-320) compared with 134 minutes (range= 100-165) for MT. All 12 patients who had an ITT experienced adverse effects such as dizziness, feeling unwell and clammy whilst only 1 patient who underwent MT experienced the adverse effect of dizziness. ITT required significant human and material resources including supervision from a medical practitioner, at least 2 experienced nursing staff, cardiac monitoring and hypoglycaemia rescue equipment which were not all required for MT. The overall cost of an ITT was around 700 Euros compared with 420 Euros for MT.

Discussions: ITT, whilst considered the gold-standard test for diagnosing GHD, requires substantial human and material resources and is associated with significant adverse effects which prevents its widespread utilisation in clinical practice. Additionally, the overall cost of performing an ITT, taking into account the time and resources required, is considerably more compared with MT.

Conclusion: The availability of a safer, quicker and more-tolerable GH stimulation test like MT, should no longer prevent the provision of appropriate and timely diagnosis and treatment of patients with GHD. Considering both the financial and personal burden of performing an ITT, MT should be considered as a reliable alternative as it is easy and quick to perform, associated with minimal adverse effects and has a diagnostic accuracy comparable with ITT.