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Deficientia iodi
Without iodine the thyroid cannot build its hormones — iodised salt is the simplest solution.
Also known as: iodine deficiency
Open in the tool — with search and all the links →This compilation is for information and replaces neither medical diagnosis nor treatment. If you have symptoms, see a doctor.
Iodine is not one nutrient among many, it is building material: without iodine T4 and T3 simply cannot be made — the numbers in the names stand for the iodine atoms in the molecule. The body cannot make it and stores only a little, so it has to come in from outside continuously. Where there is little in the soil there is little in vegetables and grain; Switzerland is a classic deficiency region, and the reason the topic barely shows today is iodised salt. That is exactly where the new gap lies: anyone who eats few processed foods, uses uniodised sea or rock salt at home, avoids dairy and eats no sea fish can get too little despite a very healthy diet. The body reacts quietly at first: it turns the TSH signal up to pull more out of the gland, and the gland grows — a goitre is at heart the visible attempt to make enough hormone out of little iodine. The time before and during pregnancy and while breastfeeding is critical, because the child’s brain depends on maternal thyroid hormone; the requirement then rises clearly. And the reverse holds too: a great deal of iodine, for instance from algae products, is not extra safety but a problem of its own.
Over- or underactivity should be diagnosed and treated (e.g. hormone replacement) — the key step.
Iodine is the building block of thyroid hormones; both deficiency and excess can harm. Iodised salt and sea fish cover the need.
Not every salt is iodised, and expensive sea salt, fleur de sel or rock salt generally are not. Switching to an uniodised speciality salt is the commonest unnoticed route into an inadequate supply.
Iodised table salt, dairy products and sea fish carry most of it. Anyone leaving one of these out should know where the replacement comes from.
Without milk and fish there is practically only iodised salt or a supplement left. Seaweed is not a reliable answer, because its content varies many times over between species and batch.
The requirement rises within the first weeks, when many do not yet know. With a wish for children the supply therefore belongs discussed beforehand.
Between too little and too much lies a narrow band. Very high amounts can trigger either underactivity or overactivity, depending on the gland’s history.
Turning T4 into the active T3 needs selenium, and the enzyme that builds iodine into the hormone needs iron. An iodine shortage rarely stands alone.
Iodine is built into the thyroid hormones — it fills a store that with sufficient intake lasts about three months. Iodised salt covers the requirement in normal use; sea salt and rock salt contain practically none, which is often confused. Too much iodine at once, for example from seaweed products or contrast medium, can set off over- or underactivity — more often where nodules are present. In pregnancy the requirement rises by about half.
The daily requirement is about 150 micrograms, 250 in pregnancy. The store in the thyroid lasts about three months with sufficient intake. A gram of iodised salt contains about 20 to 25 micrograms — so the usual five to six grams of salt a day cover the requirement. In Switzerland, goitre was largely made to disappear by iodised salt from the 1920s; since then the shortfall is rising again, because less salt is eaten.
It shows first at the collar or on a necklace, not in the mirror. A goitre does not hurt and grows over years.
Large glands press on gullet and windpipe. Lying down or raising the arms sometimes makes it clearer.
Only when the gland can no longer compensate do the signs of underactivity appear. Long before that only the TSH is abnormal.
Requirement and loss through the kidneys rise, and the child is supplied too. A shortage at this time affects brain development — which is why nothing is left to wait here.
A lasting shortage during growth affects height, school performance and concentration. Where supply is assured this has become rare.
If the gland grows over decades, districts form inside it that produce on their own account. So an iodine shortage can turn into overactivity in later life — the seemingly contradictory but well-known turn.
What a deficiency makes visible on the body — skin, nails, tongue, eyes and nerves. The signs are unspecific: they show where to look, they prove nothing.
If iodine is missing, the control hormone rises and drives the thyroid to grow — that is how a goitre forms, often long before the hormone values themselves are abnormal.
Iodine is the building block of this hormone — without iodine no T4. In pregnancy the need is highest, because the child depends on it.
The top timekeeper of the thyroid axis. It explains why the control is read from the top down and a single value is rarely enough.