Endocrine Abstracts

Although diminished height velocity and short stature are important clinical markers to consider testing for GHD in children, the signs and symptoms of GHD are not always so apparent in adults. Furthermore, quality of life and metabolic health are often impacted in adults with GHD; thus, making an accurate diagnosis is important so that appropriate GH replacement therapy can be offered to these patients. However, the diagnostic work up of adult GHD can be challenging and made more complicated by the episodic and pulsatile nature of endogenous GH secretion, concurrently modified by age, gender, and body mass index. Hence, GH stimulation testing is required to establish the diagnosis, and should only be considered if there is a clinical suspicion of GHD and the intention to treat if the diagnosis is confirmed. One or more GH stimulation tests may be required, but existing methods of testing can be inaccurate, difficult to perform, and imprecise. Furthermore, there are caveats when interpreting test results including individual patient factors, differences in peak GH cut-offs (by age and test) and testing time points. For now, the insulin tolerance test (ITT) remains the gold standard test, while the glucagon stimulation test is its reasonable alternative. Following its validation against the ITT, together with its safety, reproducibility and good patient tolerability, the macimorelin test gained approval in the US in December 2017 but its use was limited due to its cost and its distribution in the US was discontinued in May 2023. In Europe, macimorelin (renamed ghryvelin) was approved in January 2019 becoming the newest diagnostic test for adult GHD. Cost withstanding, given the ease of conducting this test and good patient tolerability, the oral macimorelin test has the potential of becoming the preferred GH stimulation test for diagnosing adult GHD in Europe.