Isotopes of iodine necessary in tests that require several days of imaging, for example, fibrinogen scan imaging to detect blood clots. Both I-123 and I-125 emit copious low energy Auger electrons after their decay, but these do not cause serious damage (double-stranded DNA breaks) in cells, unless the nuclide is incorporated into a medication that accumulates in the nucleus, or into DNA (this is never the case is clinical medicine, but it has been seen in experimental animal models). Iodine-125 is also commonly used by radiation oncologists in low dose rate brachytherapy in the treatment of cancer at sites other than the thyroid,
Iodine in biology no more than 70 micrograms per day to synthesize the requisite daily amounts of T4 and T3. The higher recommended daily allowance levels of iodine seem necessary for optimal function of a number of other body systems, including lactating breasts, gastric mucosa, salivary glands, oral mucosa, arterial walls, thymus, epidermis, choroid plexus and cerebrospinal fluid, among others. Iodine and thyroxine have also been shown to stimulate the spectacular apoptosis of the cells of the larval gills, tail and fins during metamorphosis in amphibians, as well as the transformation of their nervous system from that of the aquatic, herbivorous tadpole into