Iodine Loading Test
This test is used to assess whole body sufficiency for the essential element iodine.
Iodine supplementation is the daily amount of the essential element iodine needed for whole body sufficiency. Whole body sufficiency for iodine is assessed by an iodine/iodide loading test . The test consists of ingesting 4 tablets of a solid dosage form of Iodoral, containing a total of 50 mg iodine/iodide. Then urinary iodide levels are measured in the following 24 hr collection. The iodine/iodide loading test is based on the concept that the normally functioning human body has a mechanism to retain ingested iodine until whole body sufficiency for iodine is achieved. During iodine supplementation, a negative feedback mechanism is triggered that progressively adjusts the excretion of iodine to balance the intake. As the body iodine content increases, the percent of the iodine load retained decreases with a concomitant increase in the amount of iodide excreted in the 24 hr urine collection. When whole body sufficiency for iodine is achieved, the absorbed iodine/iodide is quantitatively excreted as iodide in the urine.
Since bromide competes with iodine in the body this test also tests 24 hour bromide excretion which if in excess, adversely affects iodine levels.