Iodine (urine)

The only building block of the thyroid hormones T3 and T4. Germany is one of the iodine-poor regions because its soils and groundwater contain little iodine; supply is therefore more often short here. Iodine is looked at in thyroid diagnostics.

How iodine acts in the body

Iodine is almost completely absorbed as iodide in the small intestine. The thyroid draws it from the blood via a dedicated transporter (NIS) and concentrates it strongly. There the enzyme thyroid peroxidase builds iodine into the protein thyroglobulin; this gives rise to T4 with four and T3 with three iodine atoms. Whatever is not needed is excreted by the kidneys – which is why iodine in urine reflects intake over the last few days.

Low iodine – what happens in the body?

When little iodine is available, the thyroid can make less hormone. The pituitary releases more TSH to drive it; the thyroid then takes in more iodine, preferentially makes the iodine-saving T3 and can grow under the persistent stimulus (goitre). If that is not enough, metabolism slows. In pregnancy and breastfeeding the need rises, because the child is supplied too.

High iodine – what happens in the body?

If a very large amount of iodine arrives suddenly, the thyroid temporarily reduces hormone production (Wolff-Chaikoff effect) and escapes from this after a few days. With nodules that produce hormone autonomously, however, excess iodine can trigger overactivity. High amounts come, for example, from seaweed products, X-ray contrast media or the drug amiodarone.

The interpretation is given in your report.