Macimorelin for diagnosing growth hormone deficiency

Level of innovation

The experts agreed that macimorelin is the first and only oral test approved to diagnose AGHD. Experts noted that other tests are available to diagnose AGHD, such as arginine and glucagon stimulation tests, but that these are not administered orally or work through the growth hormone secretagogue receptor.

Potential patient impact

The experts agreed that the potential patient benefits include that it is a less invasive test because of its oral administration, fewer blood samples and shorter procedure time, and that it is associated with fewer side effects. One expert noted that it may reduce travel time because it can be done at secondary district general hospitals instead of tertiary centres.

Experts identified multiple groups of people who could benefit from macimorelin, including those with a contraindication for the insulin tolerance test (for example, people with ischaemic heart disease, people aged 65 or older, and people with epilepsy) and people with uncontrolled diabetes or obesity who are at risk of test failure or inaccuracy with the insulin tolerance test and glucagon stimulation test. One expert also noted that it can be used for people who do not need their adrenocorticotropic hormone levels tested.

One expert noted that in their centre, macimorelin would be suitable for about 20 to 25 people per year. Another expert noted that their centre does about 100 insulin tolerance tests per year, but this also includes paediatrics and people who need testing for combined growth hormone and adrenocorticotropic hormone levels. The expert estimated that macimorelin would be suitable for about 1,000 to 1,500 adults per year in the UK.

Potential system impact

Experts noted multiple system benefits associated with the use of macimorelin, including that the test is less invasive; it has a shorter testing period and requires fewer blood samples to be taken and analysed, thus potentially requiring fewer staff and lab resources. Furthermore, it can be done in an outpatient setting instead of as a day case procedure. It requires fewer staff to monitor the person having the test because it does not induce hypoglycaemia, so cardiac monitoring and blood glucose monitoring are not needed. One expert noted that it has the potential to reduce waiting times because the insulin tolerance test is only offered in certain centres, leading to a delay in diagnosis and treatment for many people. All experts agreed that when considering all the costs and resources associated with doing the tests, macimorelin has the potential to be cost saving compared with standard care.

Two experts noted that tests with macimorelin can be done in most or all general hospitals. However, another expert clarified that this should be all specialist hospitals and endocrine tertiary clinics that can start and monitor growth hormone replacement therapy in adults. Experts noted that no change to existing facilities are needed. Two experts noted that it can be done in an outpatient setting, so the room needs to be suited for patient privacy and phlebotomy procedures.

Two experts agreed that training is needed because it is a new test. One expert clarified that this should be for the medical and nursing teams, mainly endocrine specialist nurses or other clinicians who have expertise in diagnosing and treating AGHD. The expert clarified that training would be so clinicians can identify the correct people for the test and inform them on what to expect from the test, and that it is not meant for mass testing. The other expert noted that the training would not be extensive because it involves a simple protocol for use.

General comments

All experts noted that macimorelin has the potential to replace some of the insulin tolerance tests or glucagon stimulation tests, specifically when these other tests are contraindicated or unable to be used because of limited resources or expertise. Two experts said that macimorelin can only test for growth hormone deficiency, but the insulin tolerance test and glucagon stimulation test are dynamic and can also diagnose adrenocorticotropic hormone deficiency by measuring the cortisol axis. This may be relevant for people after anterior pituitary surgery or radiotherapy. One expert noted that they are now moving towards using the short synacthen test, provided adrenal gland atrophy has occurred after surgery, to get information on the cortisol axes and that this cannot diagnose growth hormone deficiency. In these cases, the growth hormone axis is usually tested at a later stage, for which macimorelin could become the preferred standard of care.

The experts said that overall, there are no issues that would prevent macimorelin from being used in the NHS. However, the experts noted that the emphasis can be on the cost of macimorelin alone, rather than taking all the associated resources into account, which then may hinder adoption.

All experts noted that further research is needed, including research on its tolerability, the effect of body mass index on its effectiveness and in people for whom the insulin tolerance test is contraindicated. One expert also noted that research on the reliability of macimorelin in people with radiation-induced hypopituitarism would be valuable. One expert noted that macimorelin has not been evaluated in children yet.