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. WHO 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. ATA 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. WHO 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
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.