I have an underactive thyroid and have been told by a naturopath to start taking powdered sea kelp for iodine?

deficiency. However I have antithyroid antibodies, does this mean that my hypothyroidism isn't caused by iodine deficiency therefore I should not take it? I read on thyroidabout.com that taking sea kelp can make matters worse. Anyone taking it or has taken it and what are your thoughts on it?