I agree with Gimel.
however, in general, diet doesn't provide or really help thyroid hormones. The hormone is pretty much either produced by the thyroid gland, or it has to be supplmented with medication.
"they" say that crruciform (cabbange, califlower, brocoli, brussel sprouts etc) are "bad" for thyroid. However you also have to balance not eating these types of foods with the other benefits those same veggies offer from a nutritional and health aspect. And there I think is little evidence of the significance or impact that those veggies really have on the thyroid level. It may be that they do in fact have an effect, but it is so small that it is of no consequence.
I think lifestyle in the form of stress and general overal health has more of a combined effect on thyroid. So it is ALWAYS better to eat right and exercise and be proper weight etc for overall health. And it would seem that being in best shape as can be can at least do no harm. OVER exercise to the extreme however can and does negatively affect the metabolism of thyroid hormone. But most people do not have the problem of exercising too much to an extreme.
Before further discussion, were you diagnosed with primary hypothyroidism related to Hashimoto's Thyroiditis? What, if any, symptoms do you have now? What is your thyroid med dosage? Please post your thyroid related test results and reference ranges shown on the lab report.