Thyrotoxic myopathy the use of radioactive iodine which directly destroys the overactive thyroid gland. The thyroid gland naturally uses iodine to produce thyroxine and other hormones. It cannot distinguish between normal iodine and the radioactive version. Administering the radioactive isotope causes the thyroid to take in the lethal iodine and quickly radiation destroys it. Typically overproduction of thyroxine using radio-iodine is blocked with one dose. The drawback to this treatment is the thyroid gland is completely destroyed and patients often develop hypothyroidism. Some do so only a few months after treatment while others may not be affected for 20–30 years. Hypothyroidism patients
Iodine demonstrated that these animals could survive after eating a 14000 mg/kg dose). Excess iodine can be more cytotoxic in the presence of selenium deficiency. Iodine supplementation in selenium-deficient populations is, in theory, problematic, partly for this reason. The toxicity derives from its oxidizing properties, through which it denaturates proteins (including enzymes). Elemental iodine is also a skin irritant, and direct contact with skin can cause damage and solid iodine crystals should be handled with care. Solutions with high elemental iodine concentration, such as tincture of iodine and Lugol's solution, are capable of causing tissue damage if used in prolonged cleaning