The Periodic Table in Medicine: Elements That Diagnose, Treat and Heal

From iodine and iron to platinum chemotherapy, technetium scans, gadolinium MRI contrast and titanium implants: the elements modern medicine relies on.

Walk through a hospital and you are walking through the periodic table. The scanner in the imaging department depends on a rare earth metal. The drug in the chemotherapy drip is built around a precious metal. The hip joint in the operating theatre is a metal first used in aircraft. Even the salt in the canteen is fortified with an element your body cannot do without.

This article tours the elements that doctors use to find illness, treat it, and rebuild the body afterwards. It describes established uses only. It is not medical advice, and nothing here should be read as a recommendation about what anyone should take or do.

Elements your body needs

Iodine and the thyroid. The thyroid gland in your neck makes hormones that set the pace of your metabolism, and every molecule of those hormones contains atoms of iodine. Without enough iodine the gland swells as it struggles to keep up, producing a lump in the neck called a goitre. Iodine deficiency in early life also harms brain development. Because the soil in many inland and mountainous regions is poor in iodine, public health programmes from the 1920s onwards began adding a small amount of an iodine compound to table salt. Iodised salt is one of the cheapest and most successful health measures ever introduced. A radioactive form of the element, iodine-131, is also used by specialists to treat some thyroid conditions, because the gland concentrates iodine so effectively that the radiation is delivered exactly where it is wanted.

Iron and anaemia. Blood is red because of haemoglobin, a protein whose iron atoms grab oxygen in the lungs and release it around the body. When iron runs short the body cannot make enough healthy red blood cells, and the result is anaemia, with tiredness, breathlessness and pale skin. Iron deficiency is among the most common nutritional problems in the world. Doctors diagnose it with a blood test and treat it by finding the cause and restoring iron levels.

Calcium and bone. Bone is a living composite of protein fibres stiffened with a calcium phosphate mineral. Around a kilogram of calcium sits in an adult skeleton, and it is not just a store. Calcium ions also carry signals in nerves, trigger muscle contraction and help blood to clot. Bone density scans measure how much of this mineral is present, and low readings point to osteoporosis, a condition in which bones become fragile.

Fluoride and teeth. Tooth enamel is a close cousin of bone mineral. Fluoride ions slot into its crystal structure and make it more resistant to the acids produced by bacteria. This is why most toothpastes contain a fluoride compound, and why many water supplies have a small amount of fluoride added or occur with it naturally.

Elements as medicines

Lithium in psychiatry. Lithium is the lightest metal, and a simple lithium salt is one of the oldest treatments still used in psychiatry. An Australian doctor, John Cade, reported in 1949 that it calmed the extreme mood swings of bipolar disorder, and it remains a standard treatment today. Exactly how it works in the brain is still not fully understood. The gap between a helpful level and a harmful one is narrow, so people who take it have regular blood tests under specialist supervision.

Platinum in chemotherapy. In the 1960s an American researcher noticed that bacteria stopped dividing in an experiment that used platinum electrodes. The cause was a platinum compound that had leaked into the solution. That compound became cisplatin, a drug that binds to DNA and stops cancer cells from copying themselves. Cisplatin transformed the outlook for testicular cancer and is used against several other cancers, along with later relatives such as carboplatin.

Gold for arthritis. Gold compounds were used for much of the twentieth century to treat rheumatoid arthritis, an approach sometimes called chrysotherapy, from the Greek word for gold. They could reduce joint inflammation but had significant side effects, and they have largely been replaced by newer drugs.

Silver in wound care. Silver ions are toxic to bacteria at levels that are gentle on human tissue. Silver has been used in dressings and creams for burns and slow-healing wounds for many years, and some medical equipment is coated with it to discourage infection.

Seeing inside the body

Barium meals. X-rays pass easily through soft tissue, so the stomach and gut are almost invisible on an ordinary X-ray. A drink containing barium sulfate changes that. Barium is a heavy element that blocks X-rays, so the gut lights up in outline as the liquid passes through. Soluble barium compounds are poisonous, but barium sulfate is so insoluble that it travels through the digestive system without being absorbed.

Gadolinium in MRI. Magnetic resonance imaging uses powerful magnets and radio waves to map the hydrogen atoms in water throughout the body. To make certain tissues stand out, patients are sometimes given a contrast agent based on gadolinium. Gadolinium ions are strongly magnetic because they have seven unpaired electrons, more than any other element, and they alter the signal from nearby water. Free gadolinium is toxic, so the ion is wrapped in a molecule that holds it tightly until it is passed out of the body.

Technetium and nuclear medicine. Technetium was the first element to be made artificially, in 1937, and it has no stable form. Yet one of its isotopes, technetium-99m, is the most widely used medical radioisotope in the world. It gives off gamma rays that a camera can detect from outside the body, and it has a half-life of about six hours, long enough for a scan but short enough to fade quickly afterwards. Attached to different carrier molecules, it can be sent to bone, heart muscle or kidneys, and the resulting images, known as SPECT scans, show how organs are working rather than just what they look like. A related technique, PET scanning, most often uses a radioactive form of fluorine, fluorine-18, attached to a sugar molecule. Cancers use sugar greedily, so they show up as bright spots.

Radiation as a treatment

Radium's rise and fall. Marie and Pierre Curie discovered radium in 1898, and within a few years its radiation was being used to shrink tumours. Sealed radium sources were placed against or inside cancers, a technique that is the ancestor of modern brachytherapy. Unfortunately radium was also sold in quack tonics and used in luminous paint, and the factory workers who painted watch dials with it suffered terribly. Radium is now almost entirely retired from medicine, replaced by safer and more controllable sources.

Radon in the home. Radium's decay produces radon, a radioactive gas. Because uranium and radium occur naturally in many rocks and soils, radon seeps into buildings and can build up in poorly ventilated spaces. Breathing it over many years raises the risk of lung cancer, and it is recognised as the leading cause of lung cancer in people who have never smoked. Many countries run testing programmes, and homes with high readings can be fitted with simple ventilation systems.

Cobalt-60 and radiotherapy. From the 1950s, machines containing a source of cobalt-60 delivered focused beams of gamma rays to tumours from outside the body. The first patients were treated in Canada in 1951. In wealthier countries these units have mostly given way to linear accelerators, which produce high-energy X-rays electrically, but cobalt-60 is still used in some radiotherapy equipment and remains the standard way to sterilise huge quantities of single-use medical supplies.

Rebuilding the body

Titanium implants. Titanium is strong, light and, above all, ignored by the body. A thin oxide layer forms on its surface and stops it corroding or reacting with tissue. Better still, bone grows directly onto it, a discovery made in the 1950s and 1960s that made dental implants possible. Today titanium and its alloys form hip and knee replacements, plates and screws for broken bones, and the frames that anchor artificial teeth. A nickel and titanium alloy that springs back to a set shape is used in the tiny stents that hold blocked arteries open.

Why it matters

Medicine borrows from every region of the periodic table: light metals such as lithium, heavy metals such as barium and platinum, rare earths such as gadolinium, and radioactive elements such as technetium and cobalt-60. In each case a chemist or physicist noticed a property, such as blocking X-rays, giving off gamma rays or being tolerated by bone, and someone found a way to put it to work. Pop the bubbles on the interactive table and you will find medical uses listed for a surprising number of elements.

Key takeaways

• Iodine, iron, calcium and fluoride are elements the body needs, and iodised salt and fluoride toothpaste are simple public health uses of them.
• Lithium salts have treated bipolar disorder since the mid twentieth century, and platinum-based cisplatin is a major chemotherapy drug.
• Barium sulfate, gadolinium compounds and technetium-99m help doctors see inside the body using X-rays, MRI and gamma cameras.
• Radium pioneered radiation treatment but proved dangerous; cobalt-60 and modern accelerators replaced it, while naturally occurring radon remains a health risk in buildings.
• Titanium is used for implants because bone bonds to it and the body does not reject it.
• All of these are established uses described for interest; treatment decisions belong with qualified medical professionals.