thyroid cancer only affect thyroid function in fewer cases. most times people have it and have no thyroid malfunction at all.
i would still get it checked, i had thyroid cancer four years ago and the process to get it removed isn't as bad as you might scare yourself to be. If you are to get it removed, make sure the surgeon is a specialist- you don't want...
Portugal isn't the best place to find gluten free bread unless you speak portuguese. You could always go to one of the small bakeries and ask if their "Broa" is only made with cornmeal or if it has wheat too, but you would run too big of a risk of cross contamination (wouldn't do it).
Luckily at restaurants in the beach area you always have grilled fish...