Iodine is an essential element that is required for thyroid hormone production.
The measurement of iodine serves as an index of adequate dietary intake and iodine overload, particularly from iodine-containing drugs such as Amiodarone.
Iodine is a trace element that is naturally present in some foods, added to others, and available as a dietary supplement.
The earth’s soils contain varying amounts of iodine, which in turn affects the iodine content of crops. In some regions of the world, iodine-deficient soils are common, increasing the risk of iodine deficiency among people who consume foods primarily from those areas. Salt iodization programs, which many countries have implemented, have dramatically reduced the prevalence of iodine deficiency worldwide.
Iodine and thyroid hormones:
Iodine is an essential component of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). Thyroid hormones regulate many important biochemical reactions, including protein synthesis and enzymatic activity, and are critical determinants of metabolic activity.
They are also required for proper skeletal and central nervous system development in fetuses and infants.
Thyroid function is primarily regulated by thyroid-stimulating hormone (TSH), also known as thyrotropin. It is secreted by the pituitary gland to control thyroid hormone production and secretion, thereby protecting the body from hypothyroidism and hyperthyroidism. TSH secretion increases thyroidal uptake of iodine and stimulates the synthesis and release of T3 and T4.
In the absence of sufficient iodine, TSH levels remain elevated, leading to goiter, an enlargement of the thyroid gland that reflects the body’s attempt to trap more iodine from the circulation and produce thyroid hormones.
Other functions of iodine:
Iodine may have other physiological functions in the body as well. For example, it appears to play a role in immune response and might have a beneficial effect on mammary dysplasia and fibrocystic breast disease.
Iodine in food and iodized salt is present in several chemical forms including sodium and potassium salts, inorganic iodine, iodate, and iodide, the reduced form of iodine. Iodine rarely occurs as the element, but rather as a salt; for this reason, it is referred to as iodide and not iodine. Iodide is quickly and almost completely absorbed in the stomach and duodenum. Iodate is reduced in the gastrointestinal tract and absorbed as iodide. When iodide enters the circulation, the thyroid gland concentrates it in appropriate amounts for thyroid hormone synthesis and most of the remaining amount is excreted in the urine.
Iodine deficiencies are very common, especially in Europe and Third World countries, where the soil and food supply have low iodine levels.
Iodine is found in very few foods, which is one reason why deficiency is common. Most healthy adults need 150 mcg per day, but pregnant and lactating women need more to meet the needs of their growing babies.
Your body uses iodine to make thyroid hormones. That’s why an iodine deficiency can cause hypothyroidism, a condition in which the body can’t make enough thyroid hormones.
Luckily, deficiency is easy to prevent. Adding a dash of iodized salt or seaweed to your main meals should help you meet your requirements.
If you think you have an iodine deficiency, it’s best to talk to your doctor. They will check for visible signs of an iodine deficiency, like a goiter, or take a urine sample.
Symptoms of an iodine deficiency:
- Swelling in the front of the neck is the most common symptom of an iodine deficiency.
- Unexpected weight gain is another sign of an iodine deficiency.
- Fatigue and weakness are also common symptoms of an iodine deficiency.
- Hair loss: When your thyroid hormone levels are low, your hair follicles may stop regenerating. Over time, this may result in hair loss.
- Dry, flaky skin may affect many people with an iodine deficiency.
- Feeling cold is a common symptom of an iodine deficiency.
- Changes in heart rate
- An iodine deficiency may affect your ability to learn and remember.
- Pregnant women are at a high risk of iodine deficiency.
- Heavy and irregular menstrual bleeding may occur as a result of an iodine deficiency.
Getting high levels of iodine can cause some of the same symptoms as iodine deficiency, including goiter (an enlarged thyroid gland). High iodine intakes can also cause thyroid gland inflammation and thyroid cancer. Getting a very large dose of iodine (several grams, for example) can cause burning of the mouth, throat, and stomach; fever; stomach pain; nausea; vomiting; diarrhea; weak pulse; and coma.
The daily upper limits for iodine are listed below. These levels do not apply to people who are taking iodine for medical reasons under the care of a doctor.
|Life Stage||Upper Limit|
|Birth to 12 months:||Not established|
|Children 1–3 years:||200 mcg|
|Children 4–8 years:||300 mcg|
|Children 9–13 years:||600 mcg|
|Teens 14–18 years:||900 mcg|
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