iodine (generic name)
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CategoryHerbs & Supplements
Atomic number 53, Betadine®, cadexomer iodine, I, Iodin, iodine-125, iodine-131, iodized poppy seed oil, iodized salt, iodothyronine, iodotyrosine, KI, Licartin®, Lipiodol®, Lugol solution, Lugol's iodine, potassium iodide, polyvinylpyrrolidone-iodine, povidone-iodine, PVP-I, radioiodine, SKI, strong iodine, tincture of iodine.
Iodine is an element (atomic number 53) that 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 the 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).
EvidenceDISCLAIMER: 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.
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 the 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.
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. While iodine deficiency is not common in developed countries, it 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.
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.
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.
Povidone-iodine 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, 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 SSKI.
Hearing loss (iodine deficiency):
Auditory disturbances may be present in iodine deficient children, and continuous iodine supplementation may improve the auditory thresholds.
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.
Ophthalmia neonatorum prevention:
"Ophthalmia neonatorum" is defined as conjunctivitis with eye discharge that occurs during the first month of life. Various bacteria can cause this condition, including gonococcus andChlamydia trachomatis. Several agents have been used as drops in the eyes to prevent this condition in infants, including erythromycin, silver nitrate, gentamicin, and povidone-iodine. Tetracycline and penicillin drops have also been used. Although this condition is now uncommon in industrialized nations, it remains a problem in the developing world with an incidence as high as 20-30% and cases of blindness reported in Africa each year.
Povidone-iodine ophthalmic solution appears to have broad-spectrum activity against bacteria and is less expensive than many antibiotics. It therefore may be a cost-effective option in some populations.
There is limited research to suggest that iodine mouth rinses may decrease the severity of mucositis in the mouth related to cancer chemotherapy or radiation therapy. The management of mucositis should be discussed with the cancer care team.
Thyrotoxicosis / thyroid storm (adjunct iodides):
Hyperthyroid crisis (thyroid storm) is a medical emergency caused by excessive release of thyroid hormones into the circulation. Initial management of this condition involves inhibition of thyroid function with thioamide drugs such as propylthiouracil or methimazole. Iodides (such as potassium iodide) can then be administered to block the release of thyroid hormone, but should only be given an hour after thioamides to assure that the iodide is not used by the thyroid to make more thyroid hormone and worsen symptoms. Caution is warranted because iodide preparations carry a risk of causing serum sickness. Iodides should not be used for long-term treatment of thyrotoxicosis.
Povidone-iodine bladder irrigation has been suggested prior to catheter removal, or prior to prostatectomy surgery, to reduce the risk of infection. There is limited research in this area.
Early research suggests that povidone-iodine may control bleeding better than saline. Additional research is needed before a strong recommendation can be made.
The potential role of non-radioactive iodine in cancer care remains unknown. Antioxidant and anti-tumor effects have been proposed based on laboratory research. In contrast, some scientists have asserted that tumors may uptake more iodine than normal tissues. It has been suggested that high rates of gastric (stomach) cancer or low rates of breast cancer in coastal Japan may be due to high iodine intake, although this has not been demonstrated scientifically. Povidone-iodine solutions have been used as a part of alternative cancer regimens, such as the Hoxsey formula. Preliminary study has also indicated povidone-iodone solution as a potential rectal washout for rectal cancer. Overall, no clear conclusion can be drawn based on the currently available evidence.
Iodine is required for the production of thyroid hormones, which are necessary for normal brain development and cognition. One study showed that oral iodized oil significantly improved performance on cognitive tests in 10-12 year-old school children. Further study is needed to confirm these results.
Corpus vitreous degeneration:
Topical administration of iodine eye drops may reduce corpus vitreous degeneration. Further study is needed to confirm these results.
Iodine deficiency can cause goiter (hypertrophy of the thyroid gland). Other causes of goiter should be considered in patients with this condition, such as 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.
Initial management of goiter should involve a medical evaluation to identify the underlying cause and assessment of levels of thyroid hormones in the body. Treatment usually involves the administration of thyroid hormone, most commonly levothyroxine sodium (Synthroid, Levoxyl, Levothroid). Iodine plays a role in goiter prevention, but not in acute management of this condition. Iodine deficiency should be corrected if found with supplementation.
Povidone-iodine has been suggested as a topical treatment for molluscum. There is limited research in this area.
Gargling with povidone-iodine before oral intubation reduces the transport of bacteria into the trachea.
Vaginal douching with aqueous povidone iodine followed by normal saline irrigation immediately before oocyte retrieval seems effective in preventing the pelvic infection without compromising the outcome ofin vitrofertilization treatment.
Periodontitis / gingivitis:
Povidone-iodine mouthwash has been suggested to reduce mouth flora in the setting of periodontitis or around oral surgery. Evidence in this area is not conclusive.
Based on one prospective randomized study, regular oropharyngeal application of povidone-iodine may decrease the prevalence of ventilator-associated pneumonia in patients with severe head trauma. Evidence in this area is not conclusive.
Preoperative vaginal scrub with povidone-iodine decreases the incidence of postcesarean endometritis. This intervention does not seem to decrease the overall risk of postoperative fever or wound infection.
Renal Pelvic Instillation Sclerotherapy (RPIS):
Povidone iodine 0.2% has been shown to be as effective for RPIS as 1% silver nitrate.
It is not clear if healing of wounds or skin ulcers is improved with the application of topical iodine solutions. Iodine solutions may assist with sterilization as a part of a larger approach to the healing process.
Kidney problems (kidney cysts):
Iodine has been suggested as a possible treatment for kidney cysts, or small, fluid-filled sacs in the kidneys. Early research suggests that povidone iodine injections after kidney cysts are drained are not effective.
Visual outcomes in corneal ulceration:
Povidone-iodine does not seem to improve visual outcomes in corneal ulceration.