Iodine

Among the major uses of iodine compounds are catalysts, animal feed supplements, stabilizers, dyes, colourants and pigments, pharmaceutical .minor uses include smog inhibition, cloud seeding, and various uses in analytical chemistry. Iodine is an essential trace mineral not made by the body so must be obtained by food or supplements. It is found naturally in some foods and is added to supplements and some salt seasonings. Iodine is needed to make the thyroid hormones thyroxine and triiodothyronine. Without enough iodine, these thyroid hormones do not work properly and can lead to an under-active or overactive thyroid gland, causing the medical conditions of hypothyroidism and hyperthyroidism with various negative side effects in the body. Iodide salts are also  used in disinfectants, printing inks and to make polarising filters for LCD displays.

Iodine is one element that can act as a radioactive tracer, a substance with a radioactive isotope that emits radiation as it passes through a medium. In medical diagnostics, iodine is used in X-ray, ultrasound and nuclear imaging scans such as computerized axial tomography, or CAT, scans.