Sentence:  Besides the presence of goitrogens in the diet , the level of <WSD>iodine</WSD> itself in the diet plays a major role in governing the activity of the thyroid gland . 
Meaning of the word marked with <WSD> tags:  a nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks)