Iodine-131 (radioactive iodine) (I-131)

Iodine‑131 is a radioactive isotope of iodine used therapeutically in nuclear medicine. It emits both beta and gamma radiation. When administered orally or intravenously as sodium iodide I‑131, it is selectively taken up by the thyroid gland due to the organ’s natural affinity for iodine. The emitted beta particles cause localized cellular damage through ionization and excitation processes, leading primarily to destruction of normal or malignant thyroid tissue. This property makes it effective for treating hyperthyroidism and differentiated types of thyroid cancer such as papillary or follicular carcinoma. However, because “ionizing radiation delivered via iodine‑131” refers not to a molecular target but rather a physical process/agent used in therapy, it does not fit standard definitions for drug targets like receptors or enzymes; thus this entry should be flagged as incorrect if used as a molecular target name[1][2][3][4][5]. **Note:** “Ionizing radiation (delivered via iodine‑131)” is not itself a molecule/receptor/target but describes an energy form delivered by the radioisotope agent Iodine‑131; therefore this entry should be considered incorrect when cataloging canonical drug targets.

Other names

Radioactive iodineRAI¹³¹ISodium iodide I-131

Delivers beta and gamma ionizing radiation to thyroid tissue via selective uptake of iodide by thyroid cells, causing DNA damage and cell death[3][6][8].