Iodine in biology hormone is suppressed, the body simply eliminates excess iodine, and as a result, long-term supplementation with high doses of iodine has no additional effect once the body is replete with enough iodine. It is unknown if the thyroid gland is the rate-limiting factor in generating thyroid hormone from iodine and tyrosine, but assuming it is not, a short-term loading dose of one or two weeks at the tolerable upper intake level may quickly restore thyroid function in iodine-deficient patients. Iodine vapor is very irritating to the eye, to mucous membranes, and in the respiratory tract. Concentration of iodine in the
Iodine and iodate anions are often used for quantitative volumetric analysis, for example in iodometry and the iodine clock reaction (in which iodine also serves as a test for starch, forming a dark blue complex), and aqueous alkaline iodine solution is used in the iodoform test for methyl ketones. The iodine test for starch is still used to detect counterfeit banknotes printed on starch-containing paper. The spectra of the iodine molecule, I, consists of (not exclusively) tens of thousands of sharp spectral lines in the wavelength range 500-700 nm. It is therefore a commonly used wavelength reference (secondary standard). By measuring