Testing is very important in determining whether the child with growth retardation does indeed have growth hormone deficiency. Various agents may be used including insulin, arginine, clonidine and l-dopa. These tests are meant to stimulate the pituitary to secrete GH allowing for the testing of blood samples for the levels of GH at timed intervals.
Physicians often test for other hormone deficiencies that may be the underlying cause of short stature. FreeT4, TSH, cortisol, celiac antibodies, etc. are measured to rule out underlying organic causes of short stature.
IGF-1, a protein produced primarily by the liver but present in all tissues in response to GH stimulation, can be measured to screen for GHD and later to titrate GH therapy.
Children with severe GHD should be re-tested after completing growth to see if they meet the requirements for GH therapy as an adult.