Treatment of the thyroid gland with radioactive iodine has more advantages. Radioactive iodine How to obtain radioactive iodine 131

Iodine-131 (iodine-131, 131 I)- artificial radioactive isotope of iodine. The half-life is about 8 days, the decay mechanism is beta decay. First obtained in 1938 at Berkeley.

It is one of the significant fission products of uranium, plutonium and thorium nuclei, accounting for up to 3% of nuclear fission products. During nuclear tests and nuclear reactor accidents, it is one of the main short-lived radioactive pollutants of the natural environment. It poses a great radiation hazard to humans and animals due to its ability to accumulate in the body, replacing natural iodine.

In turn, tellurium-131 ​​is formed in natural tellurium when it absorbs neutrons from the stable natural isotope tellurium-130, the concentration of which in natural tellurium is 34 at.%:

Receipt

The main quantities of 131 I are obtained in nuclear reactors by irradiating tellurium targets with thermal neutrons. Irradiation of natural tellurium produces almost pure iodine-131 as the only final isotope with a half-life of more than a few hours.

In Russia, 131 I is produced by irradiation at the Leningrad Nuclear Power Plant in RBMK reactors. Chemical separation of 131 I from irradiated tellurium is carried out in. The production volume makes it possible to obtain the isotope in quantities sufficient to perform 2...3 thousand medical procedures per week.

Iodine-131 in the environment

The release of iodine-131 into the environment occurs mainly as a result of nuclear tests and accidents at nuclear power plants. Due to the short half-life, several months after such a release the iodine-131 content drops below the sensitivity threshold of detectors.

Iodine-131 is considered the most dangerous nuclide for human health, formed during nuclear fission. This is explained as follows:

1. Relatively high content of iodine-131 among fission fragments (about 3%).
2. The half-life (8 days), on the one hand, is long enough for the nuclide to spread over large areas, and on the other hand, small enough to ensure a very high specific activity of the isotope - approximately 4.5 PBq/g.
3. High volatility. In any accident of nuclear reactors, inert radioactive gases escape into the atmosphere first, followed by iodine. For example, during the Chernobyl accident, 100% of inert gases, 20% of iodine, 10-13% of cesium and only 2-3% of other elements were released from the reactor [ ] .
4. Iodine is very mobile in the natural environment and practically does not form insoluble compounds.
5. Iodine is a vital trace element, and, at the same time, an element whose concentration in food and water is low. Therefore, all living organisms have developed in the process of evolution the ability to accumulate iodine in their bodies.
6. In humans, most of the iodine in the body is concentrated in the thyroid gland, but it has a small mass compared to body weight (12-25 g). Therefore, even a relatively small amount of radioactive iodine entering the body leads to high local irradiation of the thyroid gland.

The main sources of radioactive iodine pollution in the atmosphere are nuclear power plants and pharmaceutical production.

Radiation accidents

The assessment of the radiological equivalent activity of iodine-131 is adopted to determine the level of nuclear events on the INES scale.

Sanitary standards for iodine-131 content

Prevention

If iodine-131 enters the body, it may be involved in the metabolic process. In this case, iodine will remain in the body for a long time, increasing the duration of irradiation. In humans, the greatest accumulation of iodine is observed in the thyroid gland. To minimize the accumulation of radioactive iodine in the body during radioactive contamination of the environment, take medications that saturate the metabolism with ordinary stable iodine. For example, potassium iodide preparation. When taking potassium iodide simultaneously with radioactive iodine, the protective effect is about 97%; when taken 12 and 24 hours before contact with radioactive contamination - 90% and 70%, respectively, when taken 1 and 3 hours after contact - 85% and 50%, more than 6 hours - the effect is insignificant. [ ]

Application in medicine

Iodine-131, like some other radioactive isotopes of iodine (125 I, 132 I), is used in medicine for the diagnosis and treatment of certain diseases of the thyroid gland:

The isotope is used to diagnose the spread and radiation therapy of neuroblastoma, which is also capable of accumulating certain iodine preparations.

In Russia, pharmaceuticals based on 131 I are produced.

see also

Notes

1. Audi G., Wapstra A. H., Thibault C. The AME2003 atomic mass evaluation (II). Tables, graphs, and references (English) // Nuclear Physics A. - 2003. - Vol. 729. - P. 337-676. -

Radioactive iodine

Among the 20 radioisotopes of iodine formed in the fission reactions of uranium and plutonium, a special place is occupied by 131-135 I (T 1/2 = 8.04 days; 2.3 hours; 20.8 hours; 52.6 minutes; 6.61 hours), characterized by a high yield in fission reactions, high migration ability and bioavailability. During normal operation of nuclear power plants, emissions of radionuclides, including radioisotopes of iodine, are small. In emergency conditions, as evidenced by major accidents, radioactive iodine, as a source of external and internal irradiation, was the main damaging factor in the initial period of the accident.

Simplified diagram of the breakdown of iodine-131. The decay of iodine-131 produces electrons with energies up to 606 keV and gamma rays, mainly with energies of 634 and 364 keV.

The main source of radioiodine for the population in areas of radionuclide contamination was local food products of plant and animal origin. A person can receive radioiodine through the following chains:

• plants → people,
• plants → animals → humans,
• water → hydrobionts → humans.

Milk, fresh dairy products and leafy vegetables with surface contamination are usually the main source of radioiodine for the population. The absorption of the nuclide by plants from the soil, given its short lifespan, is of no practical importance.

In goats and sheep, the radioiodine content in milk is several times higher than in cows. Hundredths of incoming radioiodine accumulate in animal meat. Radioiodine accumulates in significant quantities in bird eggs. The accumulation coefficients (exceeding the content in water) of 131 I in marine fish, algae, and mollusks reach 10, 200-500, 10-70, respectively.

The isotopes 131-135 I are of practical interest. Their toxicity is low compared to other radioisotopes, especially alpha-emitting ones. Acute radiation injuries of severe, moderate and mild degrees in an adult can be expected with oral intake of 131 I in amounts of 55, 18 and 5 MBq/kg body weight. The toxicity of the radionuclide during inhalation is approximately two times higher, which is associated with a larger area of ​​contact beta irradiation.

All organs and systems are involved in the pathological process, especially severe damage to the thyroid gland, where the highest doses are formed. Radiation doses to the thyroid gland in children due to its small mass when receiving the same amounts of radioiodine are significantly higher than in adults (the mass of the gland in children, depending on age, is 1:5-7 g, in adults – 20 g).

Radioactive iodine contains much detailed information about radioactive iodine, which, in particular, may be useful to medical professionals.

Radioactive cesium

Radioactive cesium is one of the main dose-forming radionuclides of fission products of uranium and plutonium. The nuclide is characterized by a high migration ability in the external environment, including food chains. The main source of radiocesium for humans is food of animal and plant origin. Radioactive cesium supplied to animals with contaminated feed mainly accumulates in muscle tissue (up to 80%) and in the skeleton (10%).

After the decay of radioactive isotopes of iodine, the main source of external and internal radiation is radioactive cesium.

In goats and sheep, the content of radioactive cesium in milk is several times higher than in cows. It accumulates in significant quantities in bird eggs. The accumulation coefficients (exceeding the content in water) of 137 Cs in the muscles of fish reaches 1000 or more, in mollusks - 100-700,
crustaceans – 50-1200, aquatic plants – 100-10000.

The intake of cesium to humans depends on the nature of the diet. Thus, after the Chernobyl accident in 1990, the contribution of various products to the average daily intake of radiocesium in the most contaminated areas of Belarus was as follows: milk - 19%, meat - 9%, fish - 0.5%, potatoes - 46%, vegetables - 7.5%, fruits and berries – 5%, bread and bakery products – 13%. Increased levels of radiocesium are recorded in residents who consume large quantities of “gifts of nature” (mushrooms, wild berries and especially game).

Radiocesium, entering the body, is distributed relatively evenly, which leads to almost uniform irradiation of organs and tissues. This is facilitated by the high penetrating ability of gamma rays of its daughter nuclide 137m Ba, equal to approximately 12 cm.

In the original article by I.Ya. Vasilenko, O.I. Vasilenko. Radioactive cesium contains much detailed information about radioactive cesium, which, in particular, may be useful to medical professionals.

Radioactive strontium

After the radioactive isotopes of iodine and cesium, the next most important element, the radioactive isotopes of which make the greatest contribution to pollution, is strontium. However, the share of strontium in irradiation is much less.

Natural strontium is a trace element and consists of a mixture of four stable isotopes 84 Sr (0.56%), 86 Sr (9.96%), 87 Sr (7.02%), 88 Sr (82.0%). According to its physicochemical properties, it is an analogue of calcium. Strontium is found in all plant and animal organisms. The adult human body contains about 0.3 g of strontium. Almost all of it is in the skeleton.

Under normal operating conditions of a nuclear power plant, radionuclide emissions are insignificant. They are mainly caused by gaseous radionuclides (radioactive noble gases, 14 C, tritium and iodine). During accidents, especially large ones, releases of radionuclides, including strontium radioisotopes, can be significant.

89 Sr is of greatest practical interest (T 1/2 = 50.5 days) and 90 Sr (T 1/2 = 29.1 years), characterized by high yield in fission reactions of uranium and plutonium. Both 89 Sr and 90 Sr are beta emitters. The decay of 89 Sr produces a stable isotope of ytrium (89 Y). The decay of 90 Sr produces beta-active 90 Y, which in turn decays to form a stable isotope of zirconium (90 Zr).

C diagram of the decay chain 90 Sr → 90 Y → 90 Zr. The decay of strontium-90 produces electrons with energies up to 546 keV, and the subsequent decay of ytrium-90 produces electrons with energies up to 2.28 MeV.

In the initial period, 89 Sr is one of the components of environmental pollution in areas of nearby radionuclide fallout. However, 89 Sr has a relatively short half-life and, over time, 90 Sr begins to predominate.

Animals receive radioactive strontium mainly through food and, to a lesser extent, through water (about 2%). In addition to the skeleton, the highest concentration of strontium is observed in the liver and kidneys, the minimum is in muscles and especially in fat, where the concentration is 4–6 times lower than in other soft tissues.

Radioactive strontium is classified as an osteotropic biologically hazardous radionuclide. As a pure beta emitter, it poses the main danger when it enters the body. The population mainly receives the nuclide through contaminated products. The inhalation route is less important. Radiostrontium selectively deposits in bones, especially in children, exposing the bones and the bone marrow they contain to constant radiation.

Everything is described in detail in the original article by I.Ya. Vasilenko, O.I. Vasilenko. Radioactive strontium.

Iodine-131 decay diagram (simplified)

Iodine-131 (iodine-131, 131 I), also called radioiodine(despite the presence of other radioactive isotopes of this element), is a radioactive nuclide of the chemical element iodine with atomic number 53 and mass number 131. Its half-life is about 8 days. Found its main application in medicine and pharmaceuticals. It is also a major fission product of uranium and plutonium nuclei, which pose a risk to human health and have contributed significantly to the adverse health effects of the 1950s nuclear testing and Chernobyl accident. Iodine-131 is a significant fission product of uranium, plutonium and, indirectly, thorium, accounting for up to 3% of nuclear fission products.

Standards for iodine-131 content

Treatment and prevention

Application in medical practice

Iodine-131, like some radioactive isotopes of iodine (125 I, 132 I), are used in medicine for the diagnosis and treatment of thyroid diseases. According to radiation safety standards NRB-99/2009 adopted in Russia, discharge from the clinic of a patient treated with iodine-131 is permitted when the total activity of this nuclide in the patient’s body decreases to a level of 0.4 GBq.

see also

Notes

Links

• Patient brochure on radioactive iodine treatment From the American Thyroid Association

Iodine is a chemical that was discovered back in 1811 by French chemist Bernard Courtois by mixing seaweed ash and sulfuric acid. A couple of years later, his compatriot, the chemist Gay-Lussac, studied the resulting substance in more detail and proposed the name “iodine.” Translated from Greek, “iodine” means “violet”, due to the appearance of a violet color when it burns.

Iodine and the thyroid gland

The main function of the thyroid gland is to produce the hormone thyroxine. Thyroxine is a very important hormone in

our body, participating in all metabolic processes, supporting the functioning of muscles, brain and all internal organs. Thyroxine can be compared to fuel for the body, like gasoline for a car. Thyroxine is formed in the cells of the thyroid gland with the participation of iodine and the amino acid tyrosine. There are four iodine atoms in the thyroxine molecule. The peculiarity of thyroid cells is that they have the ability to capture iodine from the bloodstream and transport it inside the follicle (the structural unit of the thyroid gland). Already inside the follicle, under the action of special enzymes, thyroxine is formed from the amino acid tyrosine and four iodine atoms. Treatment with radioactive iodine is based on the ability of thyroid cells to take up iodine.

What is radioactive iodine

Each chemical element has one or more isotopes, the nuclei of which are unstable and, when radioactively decay, produce electromagnetic radiation, which can be alpha, beta or gamma. Isotopes are chemical elements that have the same number of protons, but different numbers of neutrons, and the isotopes differ from each other in physical properties. There are 37 known isotopes of iodine. I-127 is stable, and the most commonly used isotopes of radioactive iodine in medicine are I-131, I-123, I-124. Iodine is usually denoted by the letter I. When denoting an isotope, next to the letter I indicate the number of protons and neutrons in its atom. It is important to note that the number of protons in an iodine atom is constant - there are always 53 of them. If we are talking about the isotope of radioactive iodine 131 (I-131), this means that its atom contains 53 protons and 78 neutrons (their sum is 131, which is indicated in the digital part of the isotope designation). If iodine is 123, then its atom also has 53 protons, but already 70 neutrons, etc. It is the number of neutrons that determines the properties of the isotope and, as a result, various diagnostic and therapeutic purposes. An important characteristic of radioactive iodine is its half-life. So, for example, for I-131 this period is 8 days, for I-124 - 4 days, and for I-123 - 13 hours. The half-life is the period during which the activity of iodine decreases by half. The decay of radioactive iodine (I-131) produces xenon, beta particles and gamma radiation.

The principle of action of radioactive iodine in the treatment of thyroid cancer

Radioactive iodine treatment should only be given to patients who have had their thyroid gland completely removed.

If part or half of the thyroid gland is removed, treatment with radioactive iodine is pointless. Thyroid cells tend to take up iodine from the blood. It is important to note that thyroid cancer cells (papillary, follicular) are less active, but can also take up iodine. Tumor cells, when radioactive iodine enters them, die under the influence of beta radiation. The penetrating ability of beta radiation is from 0.6 to 2 mm, which makes it possible to destroy cells in which iodine has accumulated, but without damaging surrounding tissues. One of the goals of treatment with radioactive iodine is the destruction of residual thyroid tissue that exists even after a perfectly performed operation. Often, an endocrinologist surgeon may intentionally leave a small amount of healthy thyroid tissue in both the area of ​​the recurrent laryngeal nerve (to preserve the voice) and in the area of ​​the parathyroid glands (for their normal functioning). Thus, radioactive iodine destroys not only possible cancer metastases, but also residual thyroid tissue, which makes it possible to more accurately control the level of thyroglobulin in the postoperative period. Gamma radiation, which is produced during the decay of radioactive iodine, freely penetrates all tissues of the body and can be recorded using a gamma camera. Gamma radiation does not have a therapeutic effect, but is used for diagnostics. The scan result indicates where in the body radioactive iodine has accumulated, which may indicate the presence of metastatic thyroid cancer. As a rule, when scanning the whole body after radioiodine therapy, the accumulation of the drug is detected on the anterior surface, in the place where the thyroid gland was. Iodine also accumulates in the salivary glands, along the digestive tract and in the bladder. Sometimes iodine can accumulate in the mammary glands, which have iodine receptors in small quantities.

When scanning the whole body, it is important to check for distant metastases. Most often, metastases are detected in the lymph nodes of the neck and mediastinum, in the lungs and even in the bones.

Indications for treatment with radioactive iodine

According to international and Russian clinical guidelines, patients with thyroid cancer are divided into three risk groups. Depending on the risk group, the endocrinologist surgeon determines the need to prescribe treatment with radioactive iodine. The risk group is determined by the likelihood of distant metastases and progression of the tumor process.

Low risk group.

The low-risk group includes patients with a tumor whose size does not exceed 1–2 cm and if it does not extend beyond the thyroid gland. There are no metastases to the lymph nodes of the neck and other organs. Low-risk patients are not prescribed radioactive iodine therapy.

Medium risk group.

The average risk group includes patients with a thyroid tumor more than 2–3 cm in diameter, with invasion of the gland capsule and unfavorable histological variants. Patients in this group are usually prescribed radioactive iodine therapy. In this case, the dosage can be from 30 to 100 millicuries (mCi).

High risk group.

This group includes patients with aggressive growth of thyroid cancer, when there is growth into surrounding tissues (muscles, blood vessels, trachea), lymph nodes of the neck and there are distant metastases. Patients in this group are required to undergo treatment with radioactive iodine in a dose of 100 mCi or more.

Increased TSH levels TSH is a thyroid-stimulating hormone that is produced in the pituitary gland and normally regulates the functioning of the thyroid gland. One of the important properties of TSH is the stimulation of thyroid cell growth. TSH is also known to stimulate the growth of thyroid tumor cells. It is important to note that thyroid cancer cells take up iodine less well than healthy thyroid cells. However, with a high level of TSH, thyroid tumor cells are better able to capture radioactive iodine, and therefore are better destroyed. To increase TSH levels, two methods are used: stopping the use of L-thyroxine for four weeks or introducing recombinant TSH (an artificially created preparation of human TSH).

Stopping thyroxine

To increase TSH levels, patients are stopped taking thyroxine for a period of three to four weeks before treatment with radioactive iodine. In this case, the TSH level should become above 30 mU/l. In fact, the higher the TSH, the better the thyroid tumor cells will be destroyed. In addition to stimulating thyroid cancer cells, stopping the intake of thyroxine leads, so to speak, to “starvation” of iodine in tumor cells. After all, we must not forget that thyroxine contains four atoms of iodine, and when taking the tablet, the tumor cells take part of this iodine. If iodine does not enter the body within three to four weeks, then the tumor cells, when radioactive iodine is harmful to them, begin to actively capture it. As was written earlier, after radioactive iodine enters the cell, its destruction occurs.

The main disadvantage of thyroxine withdrawal is the occurrence of hypothyroidism. Hypothyroidism is a deficiency of thyroid hormones that can be accompanied by a variety of symptoms. It is important to note that the manifestation of hypothyroidism during the withdrawal of thyroxine before treatment with radioactive iodine manifests itself differently in all patients. There are patients who practically do not feel the withdrawal of thyroxine, while at the same time there are patients who, already two weeks after discontinuation of the drug, complain of sudden weakness, apathy and swelling of the face or other manifestations of hypothyroidism.

Manifestations of hypothyroidism:

Leather: may be dry, pale and cold to the touch.

Hair: become brittle and fall out.

Gastrointestinal tract: patients feel a decrease in appetite, taste, and possibly constipation.

Respiratory system: Some patients may experience weakness of the diaphragm and, as a result, breathing problems (shortness of breath, weakness of breathing).

Nervous system: memory deterioration and decreased attention, the appearance of headaches, and the possible development of depressive states.

The cardiovascular system: the pulse becomes rare (bradycardia), mild arterial hypertension (increased blood pressure) may occur, and atherosclerosis may progress in some patients.

Hematopoietic system: mild anemia (low hemoglobin levels in the blood) and increased bleeding time from cuts and injuries may occur.

Muscular system: With hypothyroidism, patients feel weakness in the muscles, and physical activity is difficult to bear. It is important to note that after starting to take thyroxine, the symptoms that arose against the background of hypothyroidism disappear and, with the correct dosage, do not reappear.

Use of recombinant TSH

Recombinant TSH is TSH in the form of a pharmacological drug for intravenous administration, which has been synthesized artificially. The use of recombinant TSH is the second way to increase TSH levels in the patient's body before radioactive iodine treatment. Unfortunately, recombinant TSH is not registered in Russia and cannot be officially used to prepare for treatment with radioactive iodine. The closest countries where you can officially obtain recombinant TSH are Ukraine, Estonia, and Finland.

Low iodine diet (iodine-free diet)

All patients are prescribed an iodine-free diet in preparation for treatment with radioactive iodine. The idea of ​​an iodine-free diet is to eliminate iodized salt and foods containing iodine from the daily diet as much as possible. Daily iodine intake should be kept to a minimum, not exceeding 50 micrograms per day. The duration of the diet is from one to three weeks before radioactive iodine therapy and one to two days after treatment.

What is the effect of “fasting” and why is an iodine-free diet needed?

When recommending treatment with radioactive iodine, the specialist understands that the patient has a risk of having metastases of thyroid cancer (to the lymph nodes of the neck, lungs, liver, bones). It is important not to forget that thyroid cancer cells have lost the properties of healthy cells, but in overwhelming numbers they have not lost the ability to take up iodine.

Let's imagine a patient with metastases of thyroid cancer, for example, to the lungs. The patient limits himself to iodine consumption for one to three weeks (a mandatory step in preparing for iodine treatment is the abolition of L-thyroxine), while the entire body does not receive enough iodine. The most important thing is that thyroid cancer cells that are located in the lungs also experience a “hunger” for iodine.

Preparing for radioactive iodine therapy

The day comes to receive a dose of radioactive iodine, and the thyroid cancer cells “do not understand” whether they have received radioactive iodine or regular iodine. Against the background of prolonged “starvation”, they begin to capture radioactive iodine from the blood with greater force. The more actively cancer cells capture radioactive iodine, the more destructive it affects them. Against the background of a properly maintained iodine-free diet and withdrawal of thyroxine, the effectiveness of treatment with radioactive iodine will be maximum.

Treatment with radioactive iodine

After preparation - withdrawal of L-thyroxine (or administration of recombinant TSH) and an iodine-free diet - the required dose of iodine is determined and treatment begins directly. The dosage of radioactive iodine is determined by radiologists. There are several commonly used doses of radioactive iodine: 30, 100, and 150 mCi (mCi). The choice of one or another dosage is made depending on the prevalence and aggressiveness of thyroid cancer. For example, if the tumor has grown only into the capsule of the thyroid gland, the dose of iodine will be less than if the cancer has spread to the lymph nodes of the neck, lungs or bones. After selecting the dose of radioactive iodine under the supervision of specialists, the patient takes the drug. Radioactive iodine comes in two forms: capsule or liquid. The therapeutic and diagnostic effect of the capsule or liquid form is not fundamentally different.

It is important to note that the main routes for removing radioactive iodine from the human body are the urinary system, gastrointestinal tract, salivary and sweat glands. The patient will be given detailed recommendations on nutrition, fluid intake and personal hygiene while in the clinic and upon returning home. After receiving radioactive iodine, radiation is emitted from the patient, which to some extent can be dangerous to surrounding people. In this regard, all patients who have received a dose of radioactive iodine are explained in detail how to behave with others. The main recommendation is to avoid contact with children and pregnant women for at least a week after receiving a dose of radioactive iodine. I often hear from patients that the period of isolation from other people after treatment with radioactive iodine should be a month or more. This information is not true. I will present data prepared in 2011 by the American Thyroid Association (ATA) together with the International Commission on Radiation Protection (ICRP). The maximum period of isolation (bedsharing with pregnant women, newborns or children) of 21 days applies to patients receiving a dose of 200 mCi of radioactive iodine. At the same time, the period of isolation in the most common situations that patients encounter upon discharge from the clinic after treatment with radioactive iodine, such as going to work, communicating with friends, walking in crowded places, does not exceed one day. Patients who follow these recommendations and basic personal hygiene are not dangerous to others and can absolutely safely be in society and lead a normal lifestyle.

Regarding the timing of planning children after treatment with radioactive iodine, the following recommendations exist: for men - after 2-3 months, for women - after 6-12 months. I advise all patients who have undergone treatment with radioactive iodine to carry documents from the clinic with them for two to three months when crossing borders or inspection points equipped with radiation detection devices. During these periods, you are certainly not dangerous to anyone, but modern devices can detect radiation from you and give a signal to the relevant services. Most often, such situations occur at security checkpoints at airports, so plan your time taking into account possible delays.

The effect of radioactive iodine on the body

It is important to understand that radioactive iodine is not a vitamin complex, and its administration should be carried out strictly according to

indications, according to international and Russian clinical guidelines. Before a course of treatment with radioactive iodine, the patient should become familiar with the possible adverse effects that may occur immediately or some time after taking the radiopharmaceutical drug. The development of undesirable symptoms directly depends on the dosage of the radioiodine received. Patients can be divided into three groups, depending on the frequency of occurrence and severity of side effects. The first group may include patients who have had a diagnostic scan with small doses of radioiodine. The second group, the largest, includes patients who underwent radioiodine therapy after surgery and received a dose of iodine from 30 to 200 mCi. The third group of patients, fortunately not numerous, includes those who have repeatedly received high doses of radioactive iodine.

For diagnostic scans, the dose of radioactive iodine does not exceed 1–5 mCi, and in such cases, adverse effects are extremely rare. When treated with radioactive iodine, depending on the type of cancer, extension beyond the thyroid gland and tumor size, the dose can vary from 30 to 200 mCi. In such cases, side effects are possible, and their likelihood is higher, the higher the dose of radioactive iodine received. The most common undesirable symptoms after receiving a therapeutic dose of radioactive iodine are as follows. Swelling and pain. Some patients experience swelling in the neck (in the area where the thyroid gland used to be) after receiving a dose of radioiodine. This phenomenon can be explained by the destruction of residual thyroid tissue. At the same time, the surrounding tissues (muscles, lymph nodes, fatty tissue) react, which are involved in the swelling, increasing in size. As a rule, the swelling goes away within a few days and does not require treatment. In case of severe discomfort, the patient can be prescribed anti-inflammatory drugs with a good therapeutic effect. Nausea and vomiting. Nausea and vomiting may occur several hours or several days after receiving a treatment dose of radioactive iodine. These symptoms may manifest themselves more actively in patients with chronic diseases of the gastrointestinal tract. As a rule, in the clinic where radioactive iodine treatment is carried out, they talk about the correct water regime and, if necessary, prescribe medications that protect the stomach and intestines (antacids).

Inflammation of the salivary glands (sialoadenitis).

Humans have three paired (right and left) salivary glands. The largest is the parotid salivary gland, which is located on the side of the face - just below and in front of the ear. The other two are the submandibular and sublingual glands. The resulting therapeutic dose of radioactive iodine partially accumulates in the salivary glands and, as a result, causes their inflammation. The parotid salivary gland is most sensitive to iodine. Sialadenitis occurs in almost 30% of patients treated with radioactive iodine. The unpleasant thing is that sialadenitis can occur either a day or several months after receiving radioactive iodine. The manifestation of sialadenitis is pain and swelling in the area of ​​the salivary gland, an increase in temperature, and a decrease in the amount of saliva. The pain usually worsens when eating.

Treatment of sialadenitis is not an easy task. First of all, it is important to inform your doctor if you have problems with the salivary glands. Your doctor will definitely recommend who to turn to for help.

Depending on the situation, various treatment regimens for sialadenitis can be used. The main recommendations when it occurs are as follows:

1. The use of sour candies, chewing gums, that is, means that enhance salivation. This will lead to more active removal of radioactive iodine from the salivary glands, which should reduce the likelihood of further inflammation.

2. Consuming large amounts of fluid. When a large amount of fluid is received, a larger amount of saliva will be produced, with the current of which radioactive iodine will be better excreted.

3. Use of anti-inflammatory drugs. Anti-inflammatory drugs reduce swelling and thereby reduce pain in the salivary gland area.

4. Massage of the parotid salivary gland.

The technique for massaging the parotid salivary gland is as follows: with the fingertips, the first movement is made from the bottom up from the angle of the jaw, when the palm touches the lower jaw, the second movement of the fingers is made towards the nose. This simple manipulation improves the flow of saliva from the gland.

It is very important not to self-medicate, but to seek help from a specialist as soon as possible. As a rule, patients are consulted by a maxillofacial surgeon, who, after examination and necessary research, determines treatment tactics. Dry mouth syndrome (xerostomia). The occurrence of dry mouth after treatment with radioactive iodine massage of the parotid gland is associated with a decrease in saliva production. This symptom may occur a week or several months after the date of therapy. Then the inflammation in the salivary glands usually goes away and salivation is restored.

Change in taste. At least a third of patients experience a change in taste after treatment with radioactive iodine. For them, food may have a metallic taste or no taste at all. As a rule, changes in taste go away after a couple of weeks without special treatment.

Conjunctivitis, inflammation of the tear jellyPS.

According to some data, inflammation of the conjunctiva (the thin, smooth tissue that covers the outside of the eye) occurs in only 1-5% of patients treated with radioactive iodine. Inflammation of the lacrimal gland is also rare. If you experience any discomfort in the eye area, you should consult an ophthalmologist as soon as possible.

Hypoparathyroidism.

The parathyroid glands are responsible for the production of parathyroid hormone, which, in turn, controls calcium metabolism. Extremely rarely, decreased function of the parathyroid glands (hypoparathyroidism) may occur after receiving radioactive iodine. The main symptoms of hypoparathyroidism are tingling on the face, a sensation of pins and needles in the face and fingers. It is important not to confuse these symptoms with an exacerbation of cervical osteochondrosis. If there is the slightest doubt, you need to check the level of parathyroid hormone and ionized calcium. If the values ​​are normal, then the patient does not have hypoparathyroidism.

Hair loss (alopecia).

Unlike chemotherapy and other cancer treatments, taking radioactive iodine does not cause hair loss. Most often, hair problems are associated with low thyroid hormone levels in preparation for radioactive iodine treatment. When you resume taking L-thyroxine, complaints of hair loss disappear.

Effect on reproductive functions.

There is still no scientific data on the negative effects of radioactive iodine on conceiving or bearing children. In women after radioiodine therapy, the risk of infertility, problems with pregnancy, or the development of congenital anomalies in children is no higher than the average in the population. It is recommended to plan for children one year after radioiodine therapy.

If repeated high doses of radioiodine are expected, women may be advised to cryopreserve their own eggs, and men may be advised to cryopreserve their sperm.

The emergence of other malignant tumors.

One of the first questions that patients ask when discussing the topic of radioactive iodine treatment for thyroid cancer is: “Does radioactive iodine cause cancer in other organs?” If the total dose of radioactive iodine reaches 600 mCi or more, the patient is slightly more likely to develop leukemia (a tumor of the hematopoietic system originating from bone marrow cells) compared to the population average. A group of foreign scientists monitored more than 500 patients to identify the effect of the combined effects of radioactive iodine and external beam radiation therapy. As a result, the development of leukemia in the study group was detected in only three patients, which amounted to 0.5%. It is important to note that at present there is no convincing scientific evidence that treatment with radioactive iodine increases the risk of developing malignant tumors of any other organs.

Consultation with a specialist on radioactive iodine treatment

Everyone knows the high danger of radioactive iodine-131, which caused a lot of trouble after the accidents in Chernobyl and Fukushima-1. Even minimal doses of this radionuclide cause mutations and cell death in the human body, but the thyroid gland is particularly affected by it. The beta and gamma particles formed during its decay are concentrated in its tissues, causing severe radiation and the formation of cancerous tumors.

Radioactive iodine: what is it?

Iodine-131 is a radioactive isotope of ordinary iodine, called radioiodine. Due to its rather long half-life (8.04 days), it quickly spreads over large areas, causing radiation contamination of soil and vegetation. I-131 radioiodine was first isolated in 1938 by Seaborg and Livingood by irradiating tellurium with a flux of deuterons and neutrons. It was subsequently discovered by Abelson among the fission products of uranium and thorium-232 atoms.

Sources of radioiodine

Radioactive iodine-131 is not found in nature and enters the environment from man-made sources:

1. Nuclear power plants.
2. Pharmacological production.
3. Testing of atomic weapons.

The technological cycle of any power or industrial nuclear reactor includes the fission of uranium or plutonium atoms, during which a large number of iodine isotopes accumulate in the installations. Over 90% of the entire family of nuclides are short-lived isotopes of iodine 132-135, the rest is radioactive iodine-131. During normal operation of a nuclear power plant, the annual release of radionuclides is small due to the filtration that ensures the decay of nuclides, and is estimated by experts at 130-360 Gbq. If the seal of a nuclear reactor is breached, radioiodine, having high volatility and mobility, immediately enters the atmosphere along with other inert gases. In gas-aerosol emissions it is mostly contained in the form of various organic substances. Unlike inorganic iodine compounds, organic derivatives of the radionuclide iodine-131 pose the greatest danger to humans, since they easily penetrate through the lipid membranes of cell walls into the body and are subsequently distributed through the blood to all organs and tissues.

Major accidents that became a source of iodine-131 contamination

In total, two major accidents at nuclear power plants are known, which became sources of radioiodine contamination of large areas - Chernobyl and Fukushima-1. During the Chernobyl disaster, all the iodine-131 accumulated in the nuclear reactor was released into the environment along with the explosion, which led to radiation contamination of a zone with a radius of 30 kilometers. Strong winds and rains carried radiation throughout the world, but the territories of Ukraine, Belarus, the southwestern regions of Russia, Finland, Germany, Sweden, and Great Britain were especially affected.

In Japan, explosions at the first, second, third reactors and the fourth power unit of the Fukushima-1 nuclear power plant occurred after a strong earthquake. The failure of the cooling system resulted in several radiation leaks, leading to a 1,250-fold increase in the amount of iodine-131 isotopes in seawater 30 km from the nuclear power plant.

Another source of radioiodine is nuclear weapons testing. Thus, in the 50-60s of the twentieth century, explosions of nuclear bombs and shells were carried out in the state of Nevada in the USA. Scientists noticed that I-131 formed as a result of explosions fell out in the nearest areas, and in semi-global and global fallouts it was practically absent due to its short half-life. That is, during migrations, the radionuclide had time to decompose before falling along with precipitation onto the Earth’s surface.

Biological effects of iodine-131 on humans

Radioiodine has a high migration ability, easily penetrates the human body with air, food and water, and also enters through the skin, wounds and burns. At the same time, it is quickly absorbed into the blood: after an hour, 80-90% of the radionuclide is absorbed. Most of it is absorbed by the thyroid gland, which does not distinguish stable iodine from its radioactive isotopes, and the smallest part is absorbed by muscles and bones.

By the end of the day, up to 30% of the total incoming radionuclide is recorded in the thyroid gland, and the accumulation process directly depends on the functioning of the organ. If hypothyroidism is observed, then radioiodine is absorbed more intensively and accumulates in the thyroid tissues in higher concentrations than with reduced gland function.

Basically, iodine-131 is eliminated from the human body through the kidneys within 7 days, only a small part of it is removed along with sweat and hair. It is known that it evaporates through the lungs, but it is still not known how much of it is excreted from the body this way.

Toxicity of iodine-131

Iodine-131 is a source of dangerous β- and γ-irradiation in a ratio of 9:1, capable of causing both mild and severe radiation injuries. Moreover, the most dangerous radionuclide is considered to be one that enters the body with water and food. If the absorbed dose of radioiodine is 55 MBq/kg of body weight, acute exposure to the whole body occurs. This is due to the large area of ​​beta irradiation, which causes a pathological process in all organs and tissues. The thyroid gland is especially severely damaged, as it intensively absorbs radioactive isotopes of iodine-131 along with stable iodine.

The problem of the development of thyroid pathology also became relevant during the accident at the Chernobyl nuclear power plant, when the population was exposed to I-131. People received large doses of radiation not only by inhaling contaminated air, but also by consuming fresh cow's milk with a high content of radioiodine. Even measures taken by the authorities to exclude natural milk from sale did not solve the problem, since about a third of the population continued to drink milk obtained from their own cows.

It is important to know!
Particularly strong irradiation of the thyroid gland occurs when dairy products are contaminated with the radionuclide iodine-131.

As a result of irradiation, the function of the thyroid gland decreases with the subsequent possible development of hypothyroidism. In this case, not only the thyroid epithelium, where hormones are synthesized, is damaged, but also the nerve cells and vessels of the thyroid gland are destroyed. The synthesis of necessary hormones sharply decreases, the endocrine status and homeostasis of the whole organism are disrupted, which can serve as the beginning of the development of thyroid cancer.

Radioiodine is especially dangerous for children, since their thyroid glands are much smaller than those of an adult. Depending on the age of the child, the weight can range from 1.7 g to 7 g, while in an adult it is about 20 grams. Another feature is that radiation damage to the endocrine gland can remain latent for a long time and appear only during intoxication, illness, or during puberty.

A high risk of developing thyroid cancer occurs in children under one year of age who received a high dose of radiation with the I-131 isotope. Moreover, the high aggressiveness of tumors has been precisely established - cancer cells penetrate into surrounding tissues and vessels within 2-3 months, metastasize to the lymph nodes of the neck and lungs.

It is important to know!
In women and children, thyroid tumors occur 2-2.5 times more often than in men. The latent period of their development, depending on the dose of radioiodine received by a person, can reach 25 years or more; in children this period is much shorter - on average about 10 years.

“Useful” iodine-131

Radioiodine, as a remedy against toxic goiter and thyroid cancer, began to be used back in 1949. Radiotherapy is considered a relatively safe method of treatment; without it, patients are affected by various organs and tissues, the quality of life deteriorates and its duration decreases. Today, the I-131 isotope is used as an additional means to combat relapses of these diseases after surgery.

Like stable iodine, radioiodine accumulates and is retained for a long time by thyroid cells, which use it to synthesize thyroid hormones. As tumors continue to perform a hormone-forming function, they accumulate iodine-131 isotopes. When they decay, they form beta particles with a range of 1-2 mm, which locally irradiate and destroy thyroid cells, while surrounding healthy tissues are practically not exposed to radiation.