Sentence:  With lower levels , thyroid hypertrophy and increased thyroid blood flow enable the thyroid to accumulate a larger proportion of the daily intake of <WSD>iodine</WSD> . 
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)