Iodide (I-)

Iodide is an essential inorganic anion required for the synthesis of the thyroid hormones thyroxine (T4) and triiodothyronine (T3) (NIH ODS). It is primarily obtained through the diet and is actively concentrated in the thyroid gland by the sodium-iodide symporter (NIS) (PubChem). Within the thyroid, iodide undergoes oxidation and organification, a process catalyzed by thyroid peroxidase, to form iodinated tyrosine residues on thyroglobulin (StatPearls). Pharmacologically, iodide is used in various forms: as a nutritional supplement to prevent goiter and cretinism, as a radiopharmaceutical for imaging or ablation of thyroid tissue, and as a protective agent to block the uptake of radioactive iodine isotopes (StatPearls). High concentrations of iodide can acutely inhibit thyroid hormone synthesis and release, a phenomenon known as the Wolff-Chaikoff effect (StatPearls). Conversely, iodine deficiency is a leading cause of preventable intellectual disability and goiter worldwide (NIH ODS). Therapeutic applications of iodide isotopes, such as I-131, leverage its specific uptake for the targeted destruction of hyperactive thyroid tissue or malignant cells (PubChem). Monitoring iodide status is crucial in clinical practice, often involving measurements of urinary iodine or thyroid function tests (NIH ODS).

Other names

Iodide ionIodine anionI-Iodide(1-)

Iodide serves as a mandatory substrate for thyroid hormone biosynthesis, where it is transported into thyroid cells via the sodium-iodide symporter (NIS) and organified by thyroid peroxidase (TPO) (NIH ODS). Pharmacological doses of iodide can induce the Wolff-Chaikoff effect, which is an autoregulatory mechanism that inhibits the organification of iodide and the release of thyroid hormones (StatPearls). In the context of radiation protection, stable iodide (as potassium iodide) competitively inhibits the thyroidal uptake of radioactive iodine isotopes, thereby reducing the risk of radiation-induced thyroid cancer (StatPearls). Radioactive isotopes like I-131 act by emitting beta radiation to destroy thyroid tissue in cases of hyperthyroidism or thyroid carcinoma (PubChem).