Iodine, Random Urine

The Iodine, Random Urine test (urinary iodine; urine iodine concentration) quantifies recent iodine exposure to assess iodine nutrition. It supports evaluation of suspected iodine deficiency, which is associated with goiter, hypothyroidism, and adverse fetal and neonatal neurodevelopment, and it helps identify iodine excess that can trigger iodine-induced hypo- or hyperthyroidism. This measurement is also used to monitor intake from iodine-containing foods, dietary supplements, and medications, and to contextualize thyroid test abnormalities influenced by iodine status during the investigation of thyroid disorders.

Iodine is an essential micronutrient obtained primarily from the diet and drinking water. Absorption from the small intestine is efficient, and iodine circulates in blood both bound to proteins and as inorganic iodide; only the iodide form is transported into the thyroid. Thyroid follicular cells actively concentrate iodide against a gradient, oxidize it, and attach it to thyroglobulin to synthesize and store thyroxine (T4) and triiodothyronine (T3). Approximately two‑thirds of absorbed iodine is excreted by the kidneys, so urinary iodine serves as a practical indicator of recent intake for individuals and for population surveillance. Insufficient iodine reduces thyroid hormone production, leading to elevated TSH, thyroid hyperplasia, and goiter, and during pregnancy and early life is linked to irreversible neurodevelopmental impairment. Excess intake may precipitate iodine‑induced hypothyroidism or hyperthyroidism and can provoke mucosal or dermatologic reactions (eg, iodism or iododerma) in susceptible persons.