Shelley,

I have been taking a magnesium supplement with really good results (over the years, I have tried a number of other magnesium supplements). It is called Ionic-Fizz Magnesium Plus. I hear that Peter Gillham Natural Vitality Natural Calm magnesium is also good. I am finally getting muscles to release that have been hard and cable-like for years. Magnesium could be helpful for you in a number of ways:

For relaxing muscles - good for TOS

For sugar metabolism - good for preventing diabetes

For helping to deal with diabetic (and other?) neropathy

For dealing with stress

For thyroid issues -
"Hypothyroidism does not have to be a lifelong struggle with low energy, depression and weight gain. A therapeutic diet coupled with effective supplementation, as well as thyroid medication where appropriate, can reduce symptoms, regulate hormones, and re-establish healthy metabolism. Magnesium supports the conversion of T4 to the active form of hormone, T3. It will also help with any fibromyalgia symptoms that you may have associated with your thyroid disease. "

In addition you might want to avoid soy products.
"Do Soy Foods Negatively Affect Your Thyroid? A Look at the Downsides of Soy":

http://www.thyroid-info.com/articles/soydangers.htm