Iodine is a chemical element that many people know primarily from iodized salt in the kitchen. However, it plays a much greater role in laboratory medicine than you might think. It is used to detect diseases, make tissue visible and even kill bacteria.

What is iodine?

Iodine is a dark, shiny element that often occurs naturally in seawater or certain soils. In the body, we need it primarily for the thyroid gland, which uses iodine to produce hormones that control our metabolism. Too little iodine can lead to problems such as goitre or tiredness, too much is not good either. In laboratory medicine, these properties and the chemical versatility of iodine are used for very different purposes.

Iodine as a colorant makes tissue visible

One of the most common uses of iodine is the staining of samples. When doctors or scientists examine tissue under a microscope – for example during a biopsy – they first have to make the cells visible. Iodine comes into play here because it binds well with certain structures in the cells. Iodine is used as a “mordant” in the so-called Gram stain, a method used to distinguish bacteria. It helps to fix a purple color in certain bacteria so that you can tell whether they have a thick or thin cell wall. This is important for deciding which antibiotics might work.

Iodine is also an aid in histology, i.e. the study of tissue. It is often combined with other dyes to clearly highlight cell nuclei or other structures. This allows pathologists to see whether cells are normal or altered in cancer examinations, for example.

Iodine in diagnostics: thyroid gland and more

Because iodine is so closely linked to the thyroid gland, laboratory medicine also uses it to detect thyroid disorders. One example is the iodine uptake test. Here, radioactive iodine – a special form that emits weak radiation – is given to the patient. A scanner then measures how much iodine the thyroid gland absorbs. If it is too much, this could indicate hyperthyroidism, as in Graves’ disease. If it is too little, it could indicate hypothyroidism or even a tumor. Such tests are safe and provide important information for the diagnosis.

Iodine also plays a role in contrast agents for X-rays or CT scans. Substances containing iodine are injected into the blood vessels because they intercept X-rays well. This makes organs, vessels or tumors more clearly visible – a great advantage during operations or for monitoring progress.

Iodine as a disinfectant

Iodine has another useful property: it kills bacteria, viruses and fungi. It is therefore often used as a disinfectant in laboratories, for example in the form of iodine tincture or povidone iodine, which is also available from pharmacies. Before a blood sample or tissue sample is taken, the skin is cleaned with it to prevent germs from entering the sample or the body. In the laboratory itself, it helps to keep work surfaces clean and avoid contamination that could falsify test results.

Advantages and problems

Iodine is so popular in laboratory medicine because it is versatile, effective and relatively inexpensive. It is easy to handle and provides quick results – whether for staining, diagnostics or hygiene. But there are also limitations. Some people have an allergic reaction to iodine, for example with contrast media, which doctors need to be aware of. And in high doses or if used improperly, it can irritate the skin or tissue.

Iodine and the future of laboratory medicine

The use of iodine continues to develop. Researchers are investigating how nanoparticles containing iodine could be used to visualize or even treat tumours. New iodine-based methods could also be developed in molecular diagnostics to detect diseases even more precisely.

In summary, iodine is a real all-rounder in laboratory medicine. Whether it’s staining cells, checking the thyroid gland or killing germs – this small element has a huge significance. It combines simple chemistry with cutting-edge medicine and helps to save lives and understand health every day.

Editorial office: X-Press Journalistenbüro GbR

Gender note. The personal designations used in this text always refer equally to female, male and diverse persons. Double/triple references and gendered designations are avoided for the sake of better readability ected.