A Research Study of How Well Macimorelin Works to Find Out if Children Have a Lack of Growth Hormone and How Safe it is

Each study participant (patient) will have 5 to 6 visits in total with the study doctor. The study will last for about 1 to 4 months, dependent on how close the visits are done. At the visits 2, 3, 4 and 5, the patient will get a stimulation test done and blood samples will be taken. At those 4 visits, the patient will have either to drink a macimorelin drink, take some clonidine tablets or get an arginine infusion. In total, the patient will get 2 macimorelin, 1 clonidine and 1 arginine test done. The level of growth hormone (GH) will be measured 4 times during the clonidine and during the arginine test and 5 times during the macimorelin test. After the test, questions on the test tolerability will be captured from patients and parents. After the arginine test, a urine dipstick test is to be done by the patient at home.