I would go with the ultrasound, just to eliminate thyroid as that possibility, and ask them to run glucose, corticol, ACTH and growth hormone levels too. This would rule out any relationship with pituitary hormone problems.
In order to put weight on, you will need a calorie intake of about 2500calories per day. Ensure it is a balance of complex carbohydrates and protein. It would also be interesting to see if you have any muscle structure changes, ie muscle weakness or loss of muscle bulk in thighs and upper arms.
I appreciate that this is going on for a while, but the important serious malignancy disorders of the chest have been ruled out which is a good thing.
Regards
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