Daughter diagnosed with hypothyroidism

My 25 year old daughter was diagnosed with hypothyroid desease when she was 16. She has always been and still is very active, and watches what and how much she eats. She is on meds and her levels appear normal, but yet she can not loose the weight or at most 10 lbs. So follwoing the rules is not the problem. She has been too patient the past 9 years, now the frustration is setting in. Are there more extensive tests that can be done?