This would be a great question for Dr Lupo at the expert thyroid forum. You can find it toward the bottom rt side of this page under expert forum....just click on thyroid.
There seems to be a lot involved here with the endocrine system. Sometimes you will see a combination of Thyroid disfunction and Adrenal disfunction....they actually go hand in hand quite often. Addisons is the name of low adrenals causing low cortisol.
Possibly even the pituitary is involved? Has anyone run PTH bloodwork along with all the other tests?
Let us know what you find out. :)
You should go to a pediatric endocrinology, this boy need to do much more tests like Insulin-like growth factor 1 (IGF-1) , LH, free testosterone, ACTH, etc. and physical examination (signs of puberty, growth, thyroid, etc) He needs treatment. GH is made by the pituitary gland and is needed for growth, so if he is 15 years old, is he growing to fast?? (explains knee problem) is there any signs of puberty? I would post in the pediatic endocrinology expert forum, Dr D. Guy is very good answering this kind of problems.