J.B.
I was curious about the bone age thing that you mentioned, which I wasn't familiar with, and came across this:
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Constitutional growth delay: This condition describes children who are small for their ages but who are growing at a normal rate. They usually have a delayed "bone age," which means that their skeletal maturation is younger than their age in years. (Bone age is measured by taking an X-ray of the hand and wrist and comparing it with standard X-ray findings seen in kids the same age.)
These children don't have any signs or symptoms of diseases that affect growth. They tend to reach puberty later than their peers do, with delay in the onset of sexual development and the pubertal growth spurt. But because they continue to grow until an older age, they tend to catch up to their peers when they reach adult height. One or both parents or other close relatives often had a similar "late-bloomer" growth pattern.
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The source for the above is http://kidshealth.org/parent/medical/endocrine/growth_dis...#
Anyway...it sounds like if the growth hormones are OK that he just might take longer to grow? Do you have any family members who didn't hit a growth spurt until late adolescence? Has he always been small? My youngest is a peanut but he's been that way since birth. My in-laws are small people and he's taking after them but his growth, as slow and minimal as it is, has been consistent so there is no reason for us to worry.
I hope you get some reassuring news at your appointment.