Iodine in biology
The U.S. Food and Nutrition Board and Institute of Medicine recommended daily allowance of iodine ranges from 150 micrograms per day for adult humans to 290 micrograms per day for lactating mothers. However, the thyroid gland needs 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 (medical use)
Iodine is used to treat and prevent iodine deficiency and as an antiseptic. For iodine deficiency it can be given by mouth or injection into a muscle. As an antiseptic it may be used on wounds that are wet or to disinfect the skin before surgery.
Common side effects when applied to the skin include irritation and discoloration. When taken by mouth or injection side effects may include allergic reactions, goitre, and thyroid dysfunction. Use during pregnancy is recommended in regions where deficiency is common, otherwise it is not recommended. Iodine is an essential trace element.
In 1811, Bernard Courtois isolated iodine from seaweed while in 1820 Jean-Francois Coindet linked iodine intake to goiter size. It initially came into use as a disinfectant and for goiter. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. Table salt with iodine, known as iodized salt, is available in more than 110 countries. In areas with low dietary iodine one dose of iodine a year at 0.32 USD per dose may be recommended.