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Thyroid function testing – should we be doing more?

Thyroid function testing – should we be doing more? | Mr Vitamins
The Lancet medical journal stated in 2012 that the world is facing an “epidemic” of thyroid disease with over 200 million people world wide having a thyroid disorder.  The term “thyroid disorder” encompasses:
  • Underactive thyroid states (hypothyroidism)
  • Overactive thyroid states (hyperthyroidism)
  • Thyroid cancer
This number doesn’t include the number of people who are in the “grey area” between perfect thyroid health and thyroid disease.  People who fall into this grey area are said to have subclinical hypothyroidism or subclinical hyperthyroidism. The number of people with subclinical thyroid dysfunction is difficult to estimate as standard thyroid screening may not be adequate to detect such states.  This article will focus on the testing needed to detect subclinical hypothyroidism, which is the most common form of thyroid disorder.

What is the thyroid and where is it located ?

The thyroid is a butterfly-shaped gland that sits low on the front of the neck. Your thyroid lies below your Adam’s apple, along the front of the windpipe. It is part of the endocrine system and produces thyroid hormones.

Meet your thyroid hormones – who are they, what do they do and how are they controlled ?

Thyroid hormones affect nearly every physiological process in the body and play vital roles in our:
  • growth and development
  • basal metabolic rate and metabolism of proteins, fats and carbohydrates
  • heart function
  • digestive function
  • muscle control
  • brain function
  • bone health
The thyroid gland manufactures a number of hormones, the most important of which are:  
  • T4 (thyroxine)
  • T3 (triiodothyronine) in small amounts
  • Reverse T3 (rT3) in small amounts
The majority of T3 and rT3 are converted from T4 in the liver, kidneys and muscles.  T4 and T3 are the biologically active forms of thyroid hormone, with T3 being around 4 times as active as T4. Reverse T3 has no biological activity.  The production of thyroid hormones is regulated by the brain and anterior pituitary gland, which secrete the hormones TRH (Thyrotropin Releasing Hormone) and TSH (Thyroid Stimulating Hormone) respectively. A number of nutrients are needed in the production and function of thyroid hormones including:
  • Iodine
  • Tyrosine (an amino acid)
  • Selenium
  • Zinc

What is subclinical hypothyroidism ?

Subclinical hypothyroidism exists when the thyroid is not working to its optimal capacity but is not underactive enough for the person to be diagnosed with a medical thyroid disease.

Why is subclinical hypothyroidism so prevalent?

Subclinical hypothyroidism is so prevalent for the following reasons:
  • Widespread mineral deficiencies such as Iodine and selenium
  • Exposure to commonly encountered toxins such as those derived from plastics and those found in cosmetics. These chemicals are ubiquitous and every one of us is exposed to them. They are known as endocrine disruptors due to their ability to interfere with the regulatory processes that make our thyroid and other endocrine glands function properly.
  • Current testing and screening for thyroid function often only picks up thyroid disease and misses those whose thyroid is underactive but not yet at a point where it can be “boxed” and labelled as a certain disease.

What blood tests are usually done to assess thyroid function ?

The most common blood test marker used for assessing thyroid health is TSH (Thyroid Stimulating Hormone) which is produced by the anterior pituitary gland.  Its job is to stimulate the thyroid to make thyroxine (T4). When TSH is higher than the reference range further testing is usually done.

What blood tests can be done to detect subclinical hypothyroidism ?

The following blood test markers are useful to give a full picture of thyroid function:
  • TSH
  • FreeT4 – measures how much free usable hormone is being produced by the thyroid
  • Free T3 – measures how much of the T4 is being converted to the active T3
  • Reverse T3 – measures how much T4 is being converted to the inactive Reverse T3
  • Iodine – one of the main building blocks of thyroid hormone
  • Zinc and selenium – needed to covert T4 to the T3
  • Thyroid antibodies – if an autoimmune process is suspected

A note on TSH

The “normal” range for TSH on a blood test report is usually 0.4 - 4.5 (this can vary from lab to lab). If your result falls outside these limits thyroid disease is often suspected and further testing usually done?  

Peter Radi | Naturopath

Peter Radi is a fully qualified Naturopath, Nutritionist and Herbalist with 17 years clinical experience. After gaining his qualifications in Naturopathy, Nutrition and Herbal Medicine at Nature Care College in Sydney he went on to earn a Bachelor of Health Science Degree in Complimentary Medicine from Charles Sturt University.  Peter’s detailed naturopathic knowledge, together with his ability to find the root cause of a person’s symptoms, inspires and supports his clients to achieve the health and vitality they seek.