Introduction
Iodine is a trace element that humans can only take in through food. The daily iodine requirement of a person is between 150 and 200 micrograms. In Germany, there is relatively little iodine in the groundwater and soil, so there is a natural iodine deficiency.
99% of the iodine ingested is used by the body to produce thyroid hormones. An iodine deficiency therefore primarily affects the function of the thyroid gland. However, in Germany, a large part of the table salt is iodized, and iodine is also added to baked goods and finished products.
This has greatly improved the supply of iodine in the population; it is assumed that about 70% of the population is supplied with sufficient iodine. Iodine is excreted with the urine. Iodine deficiency is defined as an iodine excretion in the urine of less than 100 micrograms of iodine per gram of creatinine in the urine. Creatinine is a metabolic product that is also excreted in the urine and gives an indication of kidney function. Iodine is essential for the production of thyroid hormones, so an iodine deficiency can cause thyroid dysfunction.
Thyroid gland
Iodine is necessary for the production of the thyroid hormones T4 (thyroxine) and T3 (triiodothyronine). The thyroid gland absorbs iodine from the blood by means of an iodide sodium transporter. In the thyroid gland, the iodide is oxidized to iodine and then used to produce T3 and T4.
Finished T3 and T4 is stored in the thyroid until it is released. A healthy thyroid gland can store enough iodine to supply the body with enough thyroid hormones for 3 months. If the body suffers from iodine deficiency, the thyroid gland counteracts this and switches hormone production in favor of T3.
T3 contains only 3 iodine atoms, whereas T4 contains four iodine atoms. This conversion can save iodine. In the case of a severe iodine deficiency, the thyroid gland can no longer sufficiently maintain hormone production via this mechanism and the levels of T3 and T4 in the blood fall.
The low blood hormone level leads to the formation of TSH (thyroid-stimulating hormone) in the pituitary gland. TSH causes increased iodine absorption from the intestines, empties the thyroid’s stores of T3 and T4 and stimulates thyroid hormone production. TSH has a growth-promoting effect on the thyroid cells, causing swelling of the thyroid gland, also known as goiter.
As a result of a long-lasting iodine deficiency, an underfunction of the thyroid gland develops. The symptoms affect the metabolism of the connective tissue and the energy balance. The consequences are tiredness, drive disorders, concentration problems, weight gain, constipation, brittle nails, dry hair. An underfunction of the thyroid gland due to iodine deficiency can be treated well with medication.
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