If you are going to do exercising, just take steps to minimize impacts. But, the shake of the chair from banging the weights should not be a problem, at all.

So, I assume you had the slow growing thyroid cancer. Have you made any dietary changes to enhance your immune function ?

Livestrong shows some supplement interactions. Synthroid Interactions With Vitamins | LIVESTRONG.COM None are bad. They just slow or reduce the absorption of synthroid.

Separating the time you take the synthroid and the supplements should be good but you should tell your doctor and get checked to see that your levels are good. There are plenty of list about interactions. Since you will be on synthroid for life, it would be worthwhile to familiarize yourself with the the list. Here is another: Worst Pills

But, if you are an anxious person, you need the B's, D-3 and such. Plus, they will help your immune system stay strong. Read the Vitamins sticky at the top. Only the magnesium and calcium need to be taken separate of the synthroid by 4 hours. High fiber foods also should be eaten 2 hour after taking your med.

A common vegetable intense immune strengthening anti-cancer diet is high fiber and anti-inflammatory.