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What Is Hypothyroidism?

A low thyroid function affects every cell in the body, causing your entire body to slow down and resulting in a multitude of undesirable symptoms.

Sadly, low thyroid function affects millions of people around the world who are never properly diagnosed. It is 8 times more common in females than in males, and a much higher percentage of women over 60 are affected.

Thyroxine & Triiodothyronine

You’ve probably never even heard of Thyroxine or Triiodothyronine, but they are important hormones that control your metabolic processes and influence physical development.

The production of Thyroxine and Triiodothyronine is a multi-stage process that requires several parts of your body to interact correctly. If any one of these steps goes wrong, the resulting condition is likely to be Hypothyroidism, otherwise known as Low Thyroid Function or an Underactive Thyroid.

In people with normal Thyroid function, this 3-stage process is followed:

  • The hypothalamus, a portion of the brain, produces Thyrotropin Releasing Hormone (TRH).
  • TRH reaches the pituitary gland, which then produces Thyroid-Stimulating Hormone (also known as TSH or Thyrotropin).
  • TSH is released into the bloodstream, from where it tells the Thyroid gland to release Triiodothyronine (T3) and Thyroxine (T4). This is the stuff that gets your metabolism going!

Types of Hypothyroidism

Each of the above three steps can go wrong in some way and cause Hypothyroidism. Hence there are 3 different versions of the condition, as follows:


Primary Hypothyroidism occurs when a problem with the thyroid itself results in reduced Thyroxine and Triiodothyronine production.


Secondary Hypothyroidism occurs when the pituitary gland releases insufficient Thyroid Stimulating Hormone (TSH). The thyroid then receives the wrong instructions and produces reduced levels of Thyroxine and Triiodothyronine. This is normally caused by a damaged pituitary gland.


Tertiary Hypothyroidism occurs in the first stage of the thyroid hormone-producing process. The hypothalamus releases too little Thyrotropin Releasing Hormone (TRH), which then prevents the pituitary gland and thyroid from performing their jobs properly too.

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