Thought I'd chime in given that I have some expertise in the area of growth.
Forgive me if you have already answered this... Does Jack have any signs of puberty? Slow growth relative to peers can occur secondary to later than normal puberty. Later puberty is often familial* but puberty can also be delayed with chronic illness. Crohn's with ongoing inflammation and/or low BMI are definitely reasons for slow growth and delayed puberty. Sometimes slow growth or delayed puberty are the presenting symptoms of Crohn's which I take to mean that Crohn's w/o a lot of gi symptoms can still be associated with poor growth.
*(Is there a history of later than normal puberty in you (later menarche) or dad (late growth spurt)?)
Over the 4 years with 2 inches of growth, was Jack primarily normal weight or underweight? in remission or with inflammation?
Was Jack on steroids for some of these 4 years? If so, how long? Steroids certainly can slow growth if given over a long enough period of time.
The usual w/u for short stature, should be an evaluation of the growth chart, hx, physical exam, bone age of wrist, thyroid function tests, IGF-1, and other tests to r/o silent organ dysfunction/chronic illness (CBC, ESR, lfts, bun/cr, urinalysis).
I am somewhat confused by the labs that were ordered. Some (the adrenal hormones androstenedione, dheas and 17OH progesterone) seem extraneous. A single GH sample is usually not helpful since GH is secreted at night in pulses and usually low in the day. IGF-1 is usually used to screen GH def, but please note it is also low in thin/ nutritionally depleted children.