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Radio Isotopes and Study of Radio Isotopes- Sodium Iodide I131

A radioisotope is an isotope of an element that is radioactive. Additionally, they can be defined as nuclei containing an excess of energy.


A radioisotope is an isotope of an element that is radioactive. Additionally, they can be defined as nuclei containing an excess of energy or atoms containing a dangerous combination of neutrons and protons. In other words, when neutrons and protons balance out in an isotope with an unstable nucleus, radiation is released. Conversely, energy and particles are removed by these isotopes when they undergo a more stable transformation. Geiger counters or photographic film can measure the energy liberated by the form change.

The disintegration or semi-life period of each radioisotope is unique. Alpha rays (helium nuclei), beta rays (electron or positron rays), and gamma rays (electromagnetic rays) are the most common forms of energy released. Radioactive isotopes can be used medically, both unstable and artificially created. Identifying blocked blood vessels may be done with a technetium isotope, for example. In addition, chronologies can be determined from the decay of radioactive isotopes, such as the one used in archaeology (14C).

Application of radioisotopes

  • Medicine - Diagnostics and treatment of diseases, sterilization of surgical and clinical products, etc.
  • Industries and terminology - In construction, materials and welding will be reviewed, control production processes, and conduct research.
  • Art - Restoring art objects, establishing historical or artistic objects, etc.
  • Research - Sciences such as astronomy, engineering, and medicine.
  • Agriculture - Food conservation, eradication of plague, etc.
  • Pharmacology - Prior to being approved for use by the public, drugs are studied for their metabolism.
  • Archaeology - determining the age of geological events, etc.

Study of radio isotopes – sodium iodide I131

The treatment of thyroid cancer and hyperthyroidism is among the most common uses of sodium iodide I131. A radioactive anti-thyroid drug falls under the category of propylthiouracil (PTU) and methimazole (Tapazole), but it is not prescribed by doctors unlike other anti-thyroid medications. Several sodium iodide compounds, including I 131, readily absorb through the mouth and become trapped inside the thyroid gland. The thyroid gland is damaged by the irradiation caused by trapped sodium iodide I 131. In turn, this results in a reduction in thyroid gland activity, which reduces thyroid hormone production. By excreting sodium iodide, I131 through the urine, the kidneys rid the body of excess sodium iodide. Within several weeks, most of the sodium iodide absorbed by the body is lost. This radioactivity is half-life after eight days.

Uses – Treatment for hyperthyroidism and thyroid cancer may be aided by sodium iodide I131.

Side effects

Treatment with sodium iodide I 131 for hyperthyroidism usually carries mild side effects, but larger doses prescribed for thyroid cancer may cause more severe side effects. It is thought that sodium iodide I 131 causes anaemia and reduces platelets and white blood cells in the bone marrow. This can lead to acute leukaemia.

The following symptoms can also be associated with large doses of the drug:
  • Vomiting
  • Nausea
  • Itchy skin
  • Chest pain
  • Possibly death
  • Rash
  • Increased heart rate
There is a possibility of a thyroid crisis (excessive thyroid hormone release), severe inflammation of the salivary glands, and abnormal chromosomes. An array of signs and symptoms can appear on the third day after treatment, such as:
  • Cough
  • Sore throat
  • Neck tenderness
  • Pain while swallowing
Two or three months after treatment, there may be a temporary hair thinning.

A radiopharmaceutical containing, I-131 that emits beta and gamma radiation is sodium iodide I-131. As the iodide is absorbed into the body, it is released into the extracellular fluid and accumulated in the thyroid. This enables the imaging of the thyroid gland.

In addition to treating hyperthyroidism (an overactive thyroid), sodium iodide I 131 is also used to treat certain thyroid cancers. Thyroid glands are the main absorbers of this medicine. When you treat overactive thyroid glands with radioactive iodine, the radiation damages the thyroid gland to restore its normal activity. To get rid of any remaining thyroid tissue that has been affected by thyroid cancer surgery or to eliminate thyroid cancer that has spread, higher doses of radio iodide are usually administered. Radioactivity taken up by the thyroid gland when very small doses are administered helps your doctor determine whether your thyroid gland is functioning properly or locate thyroid cancer tumours. It must be administered by or under the supervision of a doctor who is specially trained in nuclear medicine or radiation oncology.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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