I know you asked about this on your other thread as well...but really seeing a counselor is probably your best bet. Hopefully someone here at !2K who has some experience with what you are going through and can talk to you about it will show up soon.
I would think your best avenue of action at this point is to see that your wife is getting what she needs to level out the depression and to be as patient as you can be. I would trust at this point that it is the depression and the thyroid issue that is causing her to be so distant. Romance and sex when you are depressed can be the furthest thing from a woman's mind when depressed I would think - and I suppose it is possible that because she is not interested that she may be distancing herself from you to keep from getting in a situation where she wants to say, "No" and thus hurting your feelings or estranging you even more.
The problem with this is - it is just my guessing. You should try to see if she will see the counselor with you as well. Maybe you can find some common ground to stand on until she starts feeling better.
I am sorry - it sounds like it is tough on you. Best wishes for her quick recovery and your happiness.