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Radioactive Iodine

Iodine is one of such elements where only one type of isotope which is stable enough to be found abundantly in nature. The stable form of iodine is iodine 127 and the number suggest that it has got 127 as mass number. The element atomic number is 53 and hence the same number of protons as well but the 127 gives the neutrons along with protons. That gives us about 74 neutrons inside the nucleus. Apart from this stable form there are other isotopic forms of iodine. These isotopic forms have unstable nucleus and makes them prone to decay quickly. 

The instability of nucleus makes these isotopic forms radiate energy spontaneously or in one word radioactive. These forms break down, or decay and form atoms of completely different elements. When these isotopic forms start decaying the nuclei of radioactive isotopes starts releasing fast moving particles and large amounts of heat and light along with other forms of radiation. We call such forms as radioactive iodine. The most common form of radioactive iodine is iodine 129. These atoms are naturally formed when xenon, a rare gas decays in nature. These can also form by radioactive activities deep inside Earth’s cavity. 

Larger amount of Iodine 129 are formed when U 238 or uranium goes for decaying. Other forms of unstable iodine isotopes can be formed artificially. These can be triggered by bombarding stable iodine atom with neutrons. Few of such bombarded neutrons stick to nucleus of stable iodine and sets off a new form of iodine isotope. The iodine 131 is formed in one of such methods. This iodine 131 is one of the long lasting artificial isotope ever formed.

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Radioactive Iodine Definition

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The instability of iodine atom nucleus turns a normal atom into its radioactive isotope. It can be triggered by neutron bombardment or can also be caused by natural activities within the Earth’s crust. The instability inside the nucleus is caused by excess of neutrons that iodine atoms usually have. The space within the nucleus is occupied by similar charged particles like protons which repel each other. The repulsion amongst protons and extra number of neutrons makes the nucleus very unstable and it starts radiating off these inform of energy spontaneously. As we can see the most stable form of iodine has lesser number of neutrons while the unstable forms have more neutrons inside the nucleus.

The radioactive form of isotopes have a very short half-life and can decay quite quickly in comparison to the stable forms. This also implies that stability of any element relates to its abundance. The more abundant an element is in nature the more stable it can be. The unstable forms can never remain or be available in nature for longer time and radiate off energy quickly to disappear or decay soon. 

Iodine 129 and iodine 131 are two natural and artificial forms of iodine 127 respectively. These isotopic forms which are unstable or radioactive in nature is necessary for several diseases that we come across every day. The thyroid gland absorbs radioactive isotopes and help get relief from tumours. The patient is allowed to swallow some of these isotopes, which moves towards the diseased thyroid and finally kills it or destroys it.

The tracing of radiation especially for iodine 129, produced by nuclear plants is used for tracing the level of radiation in both air and water. The level of iodine 129 is compared to the level of non-radioactive for of iodine 127. 

Radioactive Iodine Treatment

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Whenever thyroid carcinoma is recurrent or is found to be widespread, it is treated with radioactive iodine and in case it cannot absorb the radioactive form then it is treated with iodine radiation therapy.
  • For any papillary and follicular types the scan for the metastatic disease is done by radioactive iodine. Once the thyroid gland is removed and thyroid hormone is discontinued for some time the radioactive iodine is pushed in to check for hot spots to appear outside thyroid area which points to metastatic state. The radioactive iodine removes the microscopic metastases effectively. 
  • The external beam radiation is used for patients whose tumours usually do not absorb radioactive iodine or can remain undifferentiated. 
  • Radioactive iodine is the treatment of choice for hyperthyroidism as it is considered as effective ay to avoid the fallout of radiation.
  • Radioactive iodine may cause serious complication for ophthalmology in some cases prone to Graves disease. Similarly the administration of radioactive iodine for pregnant women can be counterproductive and hence is avoided. 
  • Apart from these the treatment by radioactive iodine is always considered by patient’s age and management of hyperthyroidism is a big problem for young adult. 
  • Long term therapy for patients with toxic multinodular goitre or solitary hyper functioning nodule should always be radioactive iodine. 
  • Radioactive iodine therapy uses a radioactive iodine form, Iodine 131 which is given either in capsule form or in liquid dose. The iodine 131 once taken in moves through bloodstream and is absorbed selectively or taken in by residual thyroid tissue and thyroid malignant cells and finally to the destructions
  • Radioactive iodine therapy is never used for pregnant women as it can cause damages to thyroid glands of the growing foetus.
  • Radioactive iodine therapy needs a gestation period of two to three days and patient is kept isolated as support staff might get contaminated. 
  • Patient is usually tagged safe only when the half-life of radioactive iodine traces are completely discharged from body.

Radioactive Iodine Risks

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Compared to all other radioactive therapy for cancer or any other deadlier diseases, radioactive iodine is considered as safe therapy. But there are several side effects which accompany this specific therapy. 

The side effects can be either considered as early stage or late stage complications but depends upon the time interval that usually lapsed between treatment completion or the onset of the symptoms.

Patients who have gone through radioactive iodine therapy can face many associated side effects. It can be just general fatigue and weight loss. But in some cases these can be of the following:
  • Radiation thyroiditis or a condition where a person might have sore throat, neck swelling along with difficulty in swallowing.
  • Cyptopenias or a condition where a person might face extreme low level of blood platelets and higher level of white blood cells in blood stream.
  • Salivary gland swelling along with tenderness which results in less production of saliva and loss of taste 
  • The therapy can also lead to infertility in men.
  • The therapy can also lead to female infertility and hence they should avoid pregnancy for a substantial period after this treatment.
  • This therapy can also lead to low level of RBC production in bone marrow which finally lead to blood cancer.

Radioactive Iodine Precautions

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Radioactive therapy for iodine as any other radioactive materials requires a series of precautions. 
  • Residual radioactive materials needs to be detected and removed by any means as it might cause long term health hazards.
  • Serum measurement is essential for better health management as minimum amount trace remaining in body after therapy can cause leukaemia on the long term.
  • Once the therapy is over a patient needs to take thyroid hormone replacement treatment for rest of life mainly because the body loses the capacity to produce natural levels of thyroid hormones.
  • Apart from the patients regular de-radiation methods the family members and nurses who look after the patient need to take extra care while handling the patient as they also become prey to the same or less level of after effects of radiation therapy.
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