I use Modifilan. It's a brown seaweed product that is wild -harvested and prepared without heat. It contains natural alginates, fucoidan and iodine. I take it for the mercury detox cpabilities of alginates and the thyroid modulation of iodine. Fucoidan stimultes the immune system. I've seen some great reduction of MS symptoms, which in my opinion are secondary symptoms of hypothyroidism.
Here's an interview with Modifilan Producer, Sergei Yimin and Mike Adam's (Newstarget Insider):