Iodine therapy for thyroid function
ATC code: H03CA01 (Potassium iodide)
Brand names – drugs
Iosat, Thyrosafe, ThyroShield
Brand names – supplements
Solgar Kelp
Supplements are not tested in clinical trials and are not registered as medications.
Potassium iodide is the standard preparation for stable iodine supplementation. Iodine is an essential substrate for thyroid hormone (T3, T4) synthesis. At physiological doses (100–200 µg), it corrects deficiency and supports normal hormone synthesis. At pharmacological doses (above 30 mg), it suppresses thyroid hormone secretion via the Wolff-Chaikoff effect and blocks thyroid uptake of radioactive iodine-131.
First line
Potassium iodide 100–200 µg daily is first-line prevention and treatment of iodine deficiency disorders. recommends universal salt iodisation as foundational population prevention. Individual supplementation is indicated in children, adolescents, and people not consuming iodised salt in regions of mild-to-moderate iodine endemicity. Russian Ministry of Health guidelines include potassium iodide as a required component of IDD prevention.
First line
Potassium iodide 200 µg daily in pregnant and lactating women is first-line prevention of iodine deficiency, maternal hypothyroidism, and foetal neuropsychological developmental disorders. 2017 gives a level A recommendation for routine iodine supplementation in populations with sub-adequate intake. Russian clinical guidelines support routine supplementation in the country's mild-to-moderate iodine endemicity.
In baseline autoimmune thyroid disease (AIT with antibodies) or after radioactive iodine treatment, doses are individualised with an endocrinologist.
Sources
First line
Potassium iodide at high dose (130 mg adult, 65 mg children 3–18 years, 32 mg children 1 month – 3 years) as a single dose or repeated courses when radioactive iodine-131 enters the environment is the only specific intervention for thyroid protection. 2017 gives a clear protocol on doses and timing. Justified only on official authorities' direction during a nuclear emergency. Self-administered “prophylactic” use without an emergency is useless and dangerous.
Not recommended
— Anti-aging and longevity: Iodine for slowing ageing or extending lifespan is not mentioned in international guidelines. The “iodine for longevity” marketing position lacks evidence. In patients without iodine deficiency and without thyroid disease, intake above the RDA increases the risk of iodine-induced hyperthyroidism and autoimmune thyroid disease.
Selenium is a cofactor for iodothyronine deiodinase, the enzyme converting T4 to active T3. In combined iodine and selenium deficiency, iodine supplementation efficacy is reduced. In patients with autoimmune thyroiditis, additional selenium use is discussed with an endocrinologist.
FDA category A at physiological doses. Supplementation at 200–250 µg daily during pregnancy and lactation is encouraged by international societies. High doses (above 500 µg daily) can cause foetal hypothyroidism and are not recommended.
Actively secreted into breast milk. Maternal supplementation at 250 µg daily ensures adequate infant iodine. High-dose potassium iodide for maternal radiation protection requires temporary breastfeeding cessation.
potassium iodide is evaluated for the following indications with varying evidence strength: Iodine prophylaxis in pregnancy and lactation (evidence tier A), Thyroid radiation protection in nuclear emergencies (evidence tier A), Iodine deficiency disorders (evidence tier A). See the full indication matrix with dosing and citations above on this page.
Common side effects of potassium iodide (≥ 1 in 100): Metallic taste, Epigastric discomfort, Skin redness and itching. See the Safety section for uncommon and serious reactions.
FDA category A. FDA category A at physiological doses. Supplementation at 200–250 µg daily during pregnancy and lactation is encouraged by international societies. High doses (above 500 µg daily) can cause foetal hypothyroidism and are not recommended.
Actively secreted into breast milk. Maternal supplementation at 250 µg daily ensures adequate infant iodine. High-dose potassium iodide for maternal radiation protection requires temporary breastfeeding cessation.
potassium iodide is contraindicated in: Hyperthyroidism of any aetiology; Nodular and multinodular toxic goitre; Dermatitis herpetiformis (Duhring disease); Pulmonary tuberculosis (at high doses); Iodine hypersensitivity. Full list in the Safety section.
the thyroid uses iodine continuously. Cyclical use with breaks has no physiological basis. Supplementation is continuous or not at all.
skin iodine grids and oral iodine drops are not effective iodine supplementation methods. Iodine dose in these approaches cannot be assessed. Use only certified preparations with a known dose.
high-dose potassium iodide (130 mg) is used only on official authorities' direction with proven release of radioactive iodine-131. Without such direction, use is useless and dangerous – it causes iodine-induced hyperthyroidism in some patients.