Iodine : Uses and Health Benefits

by MedlinePlus

Iodine is an element (atomic number 53) which is required by humans for the synthesis of thyroid hormones (triiodothyronine/T3 and thyroxine/T4).

Chronic iodine deficiency can lead to numerous health problems in children and adults, including thyroid gland dysfunction (including goiter) and various neurologic, gastrointestinal, and skin abnormalities. Iodine deficiency in pregnant or nursing mothers can lead to significant neurocognitive deficits in their infants. "Cretinism" or severe mental retardation is a rare outcome of severe iodine deficiency during early development. Growth stunting, apathy, impaired movement, or speech/hearing problems may occur. Many individuals living in developing countries may be at risk of iodine deficiency and its complications, and iodine deficiency is considered to be a preventable cause of mental retardation.

Iodine deficiency is rare in industrialized countries such as the United States, due to enrichment of table salt and cattle feed with iodine. But deficiency is common in developing countries, where supplementation may be considered.

Humans obtain iodine from their diets. The amount of iodine in food or water depends upon the amount of iodine in the local soil. Areas with mountainous (glacier) water or heavy rainfall tend to be low in iodine content, increasing the risk of iodine deficiency.

This review does not discuss medical uses of radioactive iodine or iodine contrast agents used for imaging studies such as computerized tomography (CT scanning).

Synonyms

Atomic number 53, Betadine®, cadexomer iodine, I, Iodin, iodine-125, iodine-131, iodized poppy seed oil, iodized salt, iodothyronine, iodotyrosine, KI, Lipiodol®, Lugol solution, potassium iodide (KI), polyvinylpyrrolidone-iodine, povidone-iodine, PVP-I, radioiodine, SKI, strong iodine, tincture of iodine.

Note: This review does not discuss medical uses of radioactive iodine or iodine contrast agents used for imaging studies such as computerized tomography (CT scanning).

Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Uses based on scientific evidence

Goiter prevention

Iodine deficiency is one of the causes of goiter (hypertrophy of the thyroid gland as it tries to make more thyroid hormone in the absence of iodine). Physically, goiter appears as an abnormal enlargement of the thyroid gland in the neck. Other causes of goiter include autoimmune thyroiditis, excess iodine, other hormonal disorders, radiation exposure, infectious causes, or inborn errors of metabolism. Although goiter due to low iodine intake is rare in developed countries, it may occur in regions with endemic low iodine levels. To avoid iodine deficiency in the United States, table salt is enriched with iodine ("iodized" salt), and iodine is added to cattle feed and used as a dough conditioner. Iodine supplementation is generally not recommended in developed countries where sufficient iodine intake is common, and excess iodine can actually cause medical complications (including goiter).Iodine supplementation should be considered in cases of known iodine deficiency, and should be administered with medical supervision if possible. Notably, the treatment of goiter usually involves administration of thyroid hormone, most commonly levothyroxine sodium (Synthroid, Levoxyl, Levothroid). Iodine generally does not play a role in the acute management of this condition.

Iodine deficiency

In regions with low iodine intake or cases of known deficiency, iodine enrichment of foods or supplementation should be considered. To avoid iodine deficiency in the United States, table salt is enriched with iodine ("iodized" salt), and iodine is added to cattle feed and used as a dough conditioner. Iodine deficiency is uncommon in developed countries, but is common in other parts of the world. When considering iodine enrichment or supplementation, supervision by medical personnel or public health officials is recommended due to the potential complications involved with iodine replacement in the setting of previous deprivation, particularly if considering supplementation in pregnant women or children.

Radiation emergency (potassium iodide thyroid protection)

Potassium iodide (KI) can be taken in the setting of radiation exposure in order to reduce levels of radioactive iodine uptake by the thyroid, thus reducing the risk of later development of thyroid cancer. It is important to note that KI does not provide immediate protection from radiation damage, and does not have protective effects against other complications of radiation exposure. KI can serve as a part of a general strategy in cases of radiation emergencies, in conjunction with shelter and control of foodstuffs. Many radiation emergency kits include KI.

Skin disinfectant/sterilization

Iodine is commonly used in topical disinfectant preparations for cleaning wounds, sterilizing skin before surgical/invasive procedures, or sterilizing catheter entry sites. Betadine solution, for example, contains povidone-iodine. Other topical disinfectants include alcohol and antibiotics, and iodine is sometimes used in combination with these. Commercially prepared iodine products are recommended in order to assure appropriate concentrations.

Water purification

Iodine can be used as an antimicrobial agent for the emergency purification of water. Tablets and solutions are commercially available. Effects generally occur within 15 minutes.

Bacterial conjunctivitis

Povidone-iodine solutions (for example, 1.25% ophthalmic solutions) have been used in the management of childhood bacterial conjunctivitis, and may be as effective as other anti-bacterial solutions such as neomycin-polymyxin B-gramicidin. This is not an effective treatment for viral conjunctivitis. Medical supervision is recommended.

Graves disease (adjunct iodine/iodides)

Graves disease is an immune-mediated disorder that causes hyperthyroidism. Thyroid-stimulating immunoglobulins bind to the thyroid stimulating hormone (TSH) receptor and mimic the action of thyroid TSH, and stimulate thyroid growth and thyroid hormone overproduction. Standard treatments for Graves disease target the thyroid gland (rather than the source of the disorder), and include antithyroid drugs such as propylthiouracil or methimazole, radioactive iodine to ablate (destroy) thyroid cells, or surgery to remove thyroid tissue. Beta-blocker drugs may be used to control symptoms. Iodide preparations can be used to suppress thyroid hormone release from the thyroid, such as strong iodine solution (Lugol solution), potassium iodide (SSKI), and iodinated radiographic contrast agents (sodium ipodate). Patients undergoing thyroid surgery are commonly treated preoperatively with antithyroid drugs to achieve a euthyroid state, then 10-14 days of SSKI.

Ocular surgery infection prevention / Cataract surgery antisepsis

Topical iodine solutions such as povidone-iodine are used preoperatively to sterilize prior to ophthalmologic procedures. For example, povidone-iodine solution has been studied and used preoperatively for cataract surgery antisepsis.

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