Radioiodine

Radioiodine refers to radioactive isotopes of the element iodine, used in medicine and research. The most common isotopes are iodine-131 for therapy and iodine-123, iodine-125, and iodine-124 for diagnostic imaging and scientific studies. These isotopes are produced in nuclear reactors or particle accelerators and supplied in forms suitable for oral administration or radiopharmaceutical preparations.

Medical uses center on the thyroid gland, which naturally absorbs iodide. Diagnostic procedures use gamma-emitting isotopes such as iodine-123 for thyroid imaging and function assessment, while iodine-124 is used in PET imaging to quantify uptake. Therapeutic use mainly employs iodine-131, which emits beta particles to destroy targeted thyroid tissue and also gamma radiation for imaging after treatment. Iodine-125 is used in brachytherapy for certain cancers, delivering local radiation with relatively long-term activity.

Mechanism and indications: After administration, the thyroid concentrates the radioiodine, enabling selective imaging or destruction of tissue. This makes radioiodine effective for conditions such as hyperthyroidism, Graves disease, and differentiated thyroid cancer, including ablation of remaining thyroid tissue after surgery. Dosing is individualized to maximize therapeutic benefit while minimizing exposure to surrounding organs.

Safety and regulation: Radioiodine is tightly regulated due to radiation exposure. Procedures require trained personnel, appropriate shielding, and monitoring. Patients may need restrictions on activities and precautions to limit radiation exposure to others during the excretion period. In emergencies, stable iodine can help block thyroid uptake in exposed individuals, though this is a separate precaution outside routine clinical use.