In children with short stature, the basic work-up includes taking detailed family history, especially that the majority of cases of short stature or failure to thrive are either familial in nature (as might be the case of your son since both his father and grandfather are not tall), or what is known as constitutional delay, meaning that the child will exhibit a catch-up growth phase later than his peers. Additionally, a bunch of blood tests of the thyroid hormones, growth hormone levels and others (mainly, IGF-1), and an X-ray of the left hand and wrist to assess the bone age: to check if it fits the chronological (or actual) age of the child.
If the result of IGF-1 raises the suspicion of GH deficiency, a GH stimulation test becomes indicated. During this test, an IV is inserted, through which the child is given a substance that should be able to stimulate the release of GH.
The 1st sample is drawn early in the morning.The substance is given through the IV. Several medicines are available. I think your treating physician has chosen insulin-induced hypoglycemia, which is categorized as the most powerful stimulus for GH secretion; this test carries the risk of developing hypoglycemia (low blood sugar), so the routine is that any patient undergoing this test must be closely monitored by a doctor throughout the entire process.Additional blood samples are drawn over the next few hours.This tests usually requires 2-5 hours to be completed. During the process, there should be a physician or nurse monitoring the child.