Potassium Iodide (Iodine)

Overview

Potassium iodide (KI) is a white crystalline salt composed of potassium and iodide ions, widely used as a nutritional supplement and pharmaceutical agent. It serves primarily as a source of iodine, an essential element for thyroid hormone production, which regulates metabolism and growth. Historically, KI has been added to table salt (iodized salt) to prevent iodine deficiency disorders such as goiter and hypothyroidism. Beyond nutrition, potassium iodide is critical in medical settings for protecting the thyroid gland from radioactive iodine exposure during nuclear emergencies, thereby reducing the risk of radiation-induced thyroid cancer. It also has applications in treating hyperthyroidism and as an expectorant to help clear mucus from the respiratory tract.¹²

Forms and Variations

Potassium iodide is commonly available in several forms including tablets, liquid solutions, and injectable formulations. Tablets are the most widely used form for both dietary supplementation and emergency radiation protection due to ease of administration and stability. Liquid forms are used when swallowing tablets is difficult, such as in children or patients with swallowing impairments. Injectable potassium iodide is less common and typically reserved for specific medical treatments under professional supervision. Variations may include different dosages tailored for daily supplementation versus acute radiation exposure. The choice of form depends on the intended use, patient age, and urgency of administration.³⁴

Dosage and Administration

For general iodine supplementation, potassium iodide is often administered in low doses consistent with recommended dietary allowances, typically around 150 micrograms of iodine daily for adults. In radiation emergencies, much higher doses are used to saturate the thyroid gland and block uptake of radioactive iodine. The U.S. FDA recommends a single dose of 130 mg of potassium iodide for adults, with adjusted lower doses for children and infants. Administration is usually oral, either as a tablet or liquid, and timing is critical—ideally given shortly before or immediately after exposure to radioactive iodine. Repeated dosing may be necessary depending on the duration of exposure risk. It is advised to follow public health guidelines or healthcare provider instructions for safe and effective use.²⁴

Scientific Research and Mechanism of Action

Potassium iodide works primarily by saturating the thyroid gland with stable iodine, which inhibits the gland"s uptake of radioactive iodine isotopes such as I-131. This competitive blockade reduces the thyroid"s absorption of harmful radioactive iodine released during nuclear accidents, thereby lowering the risk of radiation-induced thyroid cancer. Studies have demonstrated that timely administration of KI can significantly reduce thyroid radiation dose and subsequent cancer risk. Additionally, KI supports normal thyroid hormone synthesis by providing essential iodine, which is a critical component of thyroxine (T4) and triiodothyronine (T3). Research continues to explore its role in managing thyroid disorders such as hyperthyroidism and its expectorant properties in respiratory conditions. The compound’s high bioavailability ensures rapid absorption and effective physiological action.³⁴

Benefits and Potential Uses

Potassium iodide offers several proven health benefits. It is essential in preventing iodine deficiency, which can cause goiter, hypothyroidism, and developmental issues such as cretinism in infants. Its most critical use is in nuclear or radiological emergencies, where it protects the thyroid gland from radioactive iodine uptake, reducing the risk of thyroid cancer, especially in vulnerable populations like children and pregnant women. KI is also used therapeutically to treat hyperthyroidism by reducing thyroid hormone production and shrinking the thyroid gland. Additionally, it acts as an expectorant, helping to loosen mucus in respiratory illnesses. Emerging research suggests potential roles in detoxifying halides such as chlorides and bromides from tissues, though these uses require further validation.¹³⁴

Side Effects and Risks

Common side effects of potassium iodide include gastrointestinal discomfort, such as nausea and stomach upset, as well as allergic reactions like rash or swelling. High doses or prolonged use can lead to iodism, characterized by symptoms such as metallic taste, sore teeth and gums, headache, and salivary gland swelling. Rarely, KI can cause thyroid dysfunction, including hypothyroidism or hyperthyroidism, especially in individuals with pre-existing thyroid disease. People with iodine sensitivity, dermatitis herpetiformis, or certain autoimmune thyroid conditions should use caution. Pregnant and breastfeeding women should only use KI under medical supervision due to potential effects on fetal and infant thyroid function.¹⁴

Interactions and Precautions

Potassium iodide can interact with medications affecting thyroid function, such as antithyroid drugs, lithium, and amiodarone, potentially altering their effects. It may also interfere with radioactive iodine uptake used in diagnostic thyroid scans. Caution is advised in patients with pre-existing thyroid disorders, kidney disease, or iodine sensitivity. During medical procedures involving radioactive iodine, KI administration should be coordinated with healthcare providers to avoid interference. Pregnant women, infants, and individuals with iodine allergies require special consideration. It is important to follow official guidelines during radiation emergencies to ensure safe and effective use.³⁴

Impact on Biomarkers

Potassium iodide supplementation influences thyroid-related biomarkers by increasing serum iodine levels and supporting normal thyroid hormone synthesis. It can alter thyroid function tests, including thyroid-stimulating hormone (TSH), free T4, and free T3 levels, especially with high or prolonged dosing. In radiation exposure scenarios, KI reduces radioactive iodine uptake by the thyroid, which can be monitored via radioactive iodine scans. Regular monitoring is recommended when used therapeutically to detect any thyroid dysfunction early.⁴

Overdose and Toxicity

Excessive intake of potassium iodide can lead to iodine toxicity, presenting with symptoms such as burning of the mouth and throat, fever, abdominal pain, diarrhea, and swelling of the salivary glands. Chronic overdose may cause thyroid dysfunction, including hypothyroidism or hyperthyroidism, and iodide-induced goiter. The safe upper limit for iodine intake is generally considered to be 1,100 micrograms per day for adults, but therapeutic doses of KI in radiation emergencies are much higher and should only be used under medical supervision. Prompt medical attention is necessary if overdose is suspected.¹⁴

Disclaimer

The information provided in this document is for educational purposes only and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.