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Where do thyroid hormones come from?

The thyroid gland has a crucial role in the body. A large butterfly-shaped gland that sits just below the windpipe, it uses iodine to produce several thyroid hormones. Two of these hormones are particularly important.

  • Triiodothyronine (known as T3)
  • Thyroxine (known as T4)


Why are thyroid hormones important?

Thyroid hormones control metabolism (the process of breaking down food into energy for cells).

T3 and T4 play roles in regulating body energy, growth and the body’s use of other hormones and vitamins. They also control production of serotonin, a ‘feel-good’ hormone. There needs to be a constant level of thyroid hormone maintained to ensure that the body functions properly.


Too much thyroid hormone in the body results in Hyperthyroidism. This is a condition that causes poor concentration, fatigue, goiter (visibly enlarged thyroid gland) and heat intolerance.

A woman with goiter, a swollen thyroid gland.
Source: Wikipedia Commons (Martin Finborud)

Hyperthyroidism is treated either with anti-thryroid medications or surgery or radioactive iodine to remove the thyroid. A patient then takes thyroid hormone replacement pills for the rest of his life.

For more information, refer to the US National Library of Medicine website at http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001396/


Not enough thyroid hormone in the body results in Hypothyroidism. Depression, unintentional weight gain, sensitivity to cold and fatigue characterise this condition. Treatment involves minimal dosage of drugs used to produced more thyroid hormone and relieve symptoms.

Hypothyroidism is usually a life-long condition and pills have to be taken daily to maintain healthy thyroid levels.

For public health reasons, iodine is often put in salt. This ensures that the body has a ready source of iodine for production of these important thyroid hormones.

For more information, refer to the US National Library of Medicine website at http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001393/


Nuclear accidents

Nuclear Power Plant in Cattenom, France.
Source: Creative Commons, Stefan Kuhn.

The thyroid gland is the only place in the body that absorbs iodine.

In the event of a nuclear accident, radioactive iodine may be released which, if absorbed into the body, will cause cancer and other disease.

Taking potassium iodide (KI) tablets at the beginning of a nuclear accident will saturate the thyroid gland. This prevents it from absorbing radioactive iodine from the environment.

The dosage and timing of taking KI tablets is very important and during a disaster, public health officials are careful to give detailed instructions for the public to follow.