Radioactive iodine (RAI) dosing varies by indication. For hyperthyroidism (Graves’ disease or toxic nodules) typical doses are about 5–15 mCi (commonly 10–15 mCi). For thyroid cancer, ablation doses are often ~30–100 mCi, while treatment for metastatic disease may use higher single or cumulative doses around 100–200 mCi depending on disease extent and protocol.

After Chernobyl, people took stable iodine (potassium iodide) to saturate the thyroid and block uptake of radioactive iodine released by the reactor. Timely dosing—ideally before or within hours of exposure—reduces radioactive iodine absorption and lowers the risk of thyroid damage and cancer, especially in children and pregnant women. It does not protect against other radioactive elements or whole-body radiation.

Iodine is used to: produce thyroid hormones and prevent deficiency (iodized salt); prevent/treat goiter and developmental cognitive impairment; as topical antiseptic (povidone‑iodine) for wounds and surgical prep; emergency water disinfection; iodinated contrast for CT scans; potassium iodide to block radioactive iodine; preoperative thyroid shrinkage (Lugol's); treat superficial fungal/skin infections; supplement animal feed; and as a laboratory stain (Gram stain).

Common side effects after a 50 mCi radioactive iodine dose include neck pain or swelling and radiation thyroiditis, sialadenitis causing salivary gland pain, swelling and dry mouth, altered or metallic taste, nausea, and temporary taste/saliva changes. Hypothyroidism often develops later requiring lifelong thyroid hormone. Rare risks: transient worsening of hyperthyroid symptoms, fertility/menstrual changes, and a very small long‑term cancer risk.

Methimazole isn’t universally “better” than radioactive iodine—each has pros and cons. Methimazole controls thyroid overactivity without destroying the gland, useful for mild disease, children, and those wanting to avoid permanent hypothyroidism, but requires ongoing monitoring and has rare risks (agranulocytosis, liver injury). Radioactive iodine is often definitive but usually causes permanent hypothyroidism and can worsen Graves’ eye disease; choice is individual.

MCI stands for Mild Cognitive Impairment. It denotes a noticeable decline in cognitive abilities—memory, attention, or thinking—that is greater than expected for age but not severe enough to significantly disrupt daily life. People with MCI may remain stable, improve, or progress to dementia; medical evaluation, monitoring, and lifestyle or therapeutic interventions help determine cause and management.