What Causes Hyperthyroidism In A Person With Anorexia?

hello,My daughter (40) has a history of anorexia. She is presently very slight, but appears to be eating well.She is now having issues with hyperthyroid, which I see are interlinked. I can not ascertain whether she still is practicing anorexic behavious as that is easy to hide. All this is effecting her ability to preform work duties.what are some very simple things she can do to alleviate the problem. A dramatic diet change is not really feasible in her household. I have suggested more rest, but she is a workaholic, has three children and is studying to gain a masters.