it could be genetic if his parents are small or he could have a growth hormone deficiency. the sooner the gets evaluated the better. get his in to see a pediatric endocrinologist asap since he is 15 now. growth hormone deficiencies must be treated before his growth plates close (while he is still growing).
my 15 year old son is the size of an 8 year old and hasnt grown in 5 years. what could be causing this?