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      First of all, it is possible that thyroid problems can cause various symptoms. An individual can have symptoms associated with decreased thyroid activity or decreased sensitivity to thyroid hormones without having any abnormalities showing up in conventional analyses. We will see how and why later.

      Let's begin with an overview of the thyroid and what it does to understand how a malfunction can affect the body in a variety of ways that may seem unrelated to thyroid function.

      The Thyroid

      Located in the neck, just below the larynx, the thyroid gland controls metabolism, protein synthesis, oxygen use and the body's sensitivity to other hormones. There is a very tight communication network between the thyroid and other endocrine glands, including the pituitary and adrenal glands. 

      The thyroid performs its function through the use of various hormones, including T3 (triiodothyronine), T4 (thyroxine) and calcitonin. The thyroxine (T4) makes up about 80% of thyroid hormones and T3 about 20%. 

      Most of the T3 used in bodily functions is produced by the thyroid gland itself. But some of it is produced in the muscles, liver and kidneys through the degradation of the hormone T4. 1 

      For the purposes of this article, I will limit myself to discussing the effects associated with abnormalities in the production of hormones T3 and T4.

      Hypothyroidism – A Definition

      Hypothyroidism is the medical term used to describe reduced activity of the thyroid. This may be because the thyroid itself is less active, i.e. it produces less thyroid hormone or the body does not respond to that which it does produce efficiently. In both cases, the result is the same - slower metabolism with a consequent decrease in activity or the efficacy of various systems.

      Since the thyroid controls the activity of most body tissues - except the brain, retina, spleen, testes and lungs - any changes in thyroid activity or the bioavailability of the hormones it produces will affect virtually all tissues of the body.2 In order to gauge the effects, refer to table number 1 below. Note that these symptoms can be caused by other factors, but hypothyroidism should not be dismissed as a hypothesis even when blood tests appear to rule it out. We will return to this later.

      Table 1: Symptoms associated with hypothyroidism 3

      CardiovascularHigh cholesterol and triglyceride levels, hypertension.
      HormonalInfertility, short menstrual cycles, abundant and lengthy menstruation.
      MetabolicDifficulty losing weight, unusual weight gain, water retention, low physical energy levels.
      Osteo-integumentaryHair and/or nails break easily, hair loss, ridged nails, dry skin, joint or muscle pain.
      PsychologicalMental fatigue, difficulty concentrating, poor memory.
      OtherA feeling that something is stuck in your throat, constipation, increased sensitivity to cold (cold feet and hands). Low basal temperature.

      A feeling that something is stuck in your throat, constipation, increased sensitivity to cold (cold feet and hands). Low basal temperature.

      As we can see, a decrease in thyroid activity can have different repercussions. Of course, other disorders such as problems with the adrenal glands, a systemic fungal infection (candidiasis), nutritional deficiencies and food intolerance may cause similar systemic effects. Also, many times hypothyroidism is accompanied by one of these or other disorders either as a cause or as an effect. This is why it is so important to see a health care professional to get a proper definition of the problem.

      Three Types Of Dysfunction

      Thyroid hormone production is partially dependent on the production of TSH (Thyroid Stimulating Hormone) from the pituitary gland as well as the presence in the body of the necessary materials to produce thyroxine (T4) and triiodothyronine (T3 ). Note that here in Quebec, blood tests are not generally prescribed  to diagnose low levels of T3, only those of TSH and T4.

      Primary Hypothyroidism 4

      When thyroid hormone levels drop, the pituitary gland secretes TSH, the hormone that stimulates the thyroid. This hormone signals the thyroid to produce more hormones. 

      In primary hypothyroidism, blood tests show that the thyroid has difficulty producing enough thyroid hormones, particularly T4. It also shows as TSH levels. In other words, the pituitary gland is producing more TSH than normal in an effort to stimulate thyroid activity. The vast majority of cases of hypothyroidism are of the autoimmune type, also known as Hashimoto's thyroiditis. 5

      The onset of primary hypothyroidism could be due to an illness in the thyroid itself, such as in Hasimoto's, the presence of substances that impede thyroid activity, or a deficiency in the building blocks required to produce thyroxine.

      Secondary hypothyroidism

      In secondary hypothyroidism, the amount of thyroid hormone is low, but the hormone that stimulates the thyroid is either low or normal. The problem here is that the pituitary gland cannot produce enough TSH to stimulate the thyroid. This means the pituitary gland, not the thyroid, is at fault.

      Cell or Tissue Hypothyroidism

      In this case, the blood parameters for the production of the pituitary gland's hormone (TSH) and thyroid hormones (T3 and T4) are normal.  Although the result of the blood test is normal, there are still symptoms that can be attributed to hypothyroidism. This can also occur in patients receiving thyroid hormone replacement, e.g. Synthroid. 6 Given the complexity of cell or tissue hypothyroidism, I will devote a future article into this topic.

      Table 2: Types of Hypothyroidism

      Type Of HypothyroidismTSHT3*T4
      SecondaryNormal or lowLowLow

      Therefore, any condition that reduces thyroid activity, whether primary, secondary or cellular, can cause biochemical and metabolic changes which, in turn, can lead to a variety of symptoms including those noted in Table 1. For the purposes of this article, I will elaborate on the possible causes of primary hypothyroidism, leaving those of cell or tissue hypothyroidism for a subsequent article. 

      Primary Hypothyroidism

      Thus, primary hypothyroidism is defined by high levels of TSH and low levels of T3 and T4. There are several possible reasons why the thyroid may have difficulty producing T3 and T4.

      Hashimoto's Thyroiditis

      Most cases of hypothyroidism are associated with an autoimmune attack on the thyroid, a condition named for the Japanese researcher who identified it, Dr. Hashimoto. Hashimoto's thyroiditis can have a number of different causes:


      Chronic stress increases thyroid activity. (7, 8) When the thyroid is overactive, it can "fall" directly into hypothyroidism. 9 Or, the thyroid can be attacked by the immune system in order to reduce its hyperactivity. 10 

      In such cases, the logical approach would be to help improve the body's stress response rather than just treating the effects with thyroid hormone replacement therapy. Therefore, it is important to check the condition of the adrenals, the glands designed to cope with stress, and make any necessary changes.

      Food Intolerance

      There is growing evidence that several food intolerance, especially intolerance to gluten, plays a role in the development of Hashimoto's thyroiditis. Gluten consumption may cause immune hyperactivity and trigger a reaction against the thyroid. This hypersensitivity can occur whether the food intolerance is of the celiac or non-celiac type. 11

      If hypothyroidism is present, it would be useful to investigate the possibility of a hypersensitivity to gluten, perhaps by following a gluten-free diet for a few weeks to see if it has any effect on the patient's symptoms. 12  For more information on wheat, see my article on the topic.13

      Heavy Metals

      A number of researchers have suggested a link between various autoimmune diseases, including Hashimoto's, and heavy metal poisoning (14), even at very low doses. 15, 16 For some individuals, replacing the amalgam fillings in their teeth had a very positive effect on the symptoms of their autoimmune disease. 17  Although these "fillings" have not contained lead for many years, they do contain mercury. A hair analysis can help detect abnormal levels of heavy metals in the body. 18,19


      The presence of certain infectious agents can also damage the thyroid. Some researchers have associated the Epstein-Barr virus, which causes mononucleosis, with the subsequent development of autoimmune reactions. 20 Others have postulated an association with fungal infections, or candidiasis. 21 The presence of these infectious agents should be evaluated when hypothyroidism is present, especially when it was preceded by mononucleosis or by chronic fungal infections. 


      Last but not least, more and more studies suggest that acidosis – which occurs when the body's pH levels are too low, the body being acidic - may also cause thyroid problems, including hypothyroidism. 22 Correcting this  acidosis has given excellent results as regards the activity of the thyroid. 23

       Most studies linking acidosis with thyroid problems have been done on individuals with metabolic acidosis, a severe form of the disease. But some clinicians have observed that an excess of acidity, even in small amounts, may have a negative impact on thyroid function. 24

      It is beneficial to check whether the body of an individual with hypothyroidism is too acidic. This simple test can be done with strips of pH paper. Your health food store or natural health practitioner can usually provide it. 


      Thyroid hormones are produced from nutritional substances obtained from the food we eat. It is, therefore, very possible that a deficiency in one of these substances affects the production of thyroid hormones. 

      We are already aware of the risk of iodine deficiency and its effect on the thyroid. This is the reason why, since the 1920’s,  we have been adding iodine to salt. However, the body does not need just iodine to produce thyroid hormones. An amino acid, tyrosine, is also required as well as the trace elements, selenium and zinc. 25


      Iodine deficiency has a direct impact on the production of thyroid hormones. And, despite the fact that we add iodine to salt, some individuals may be deficient because they do not eat sea products (seaweed, seafood) that naturally contain iodine or because they avoid adding table salt to their food.  

      In all cases of hypothyroidism, it is important to check iodine levels in the blood to detect a possible deficiency. However, supplementing with high doses of iodine can be dangerous when iodine deficiency is not present.


      Tyrosine is an amino acid that, along with iodine, is the basic material of thyroid hormones. It is interesting to note that since stress causes tyrosine loss 26, the body needs more tyrosine in times of stress. 26 

      Studies have also shown that supplementing with tyrosine reduces the effects of stress on the body. 27 Moreover, a deficiency in tyrosine can cause depression in normal subjects. 28 Thus, depression, or "mental fatigue" is a possible symptom of hypothyroidism. 


      When it comes to the thyroid, one of the most important nutrients, selenium, is often overlooked. This nutrient is, by far, the most important for proper thyroid function after iodine and tyrosine. 29 The link between selenium deficiency and Hashimoto's disease is well established. 30

      Selenium deficiency can have three major effects on thyroid activity. Because it's an antioxidant, selenium protects the thyroid against damage caused by free radicals. 31 However, if thyroid cells have already been damaged then they may be less effective at producing hormones. Furthermore, as the body does not recognize these abnormal cells, damaged thyroid tissue can become prone to an autoimmune attack. Finally, selenium, like zinc, is required for the conversion of T4 to T3. 32 Selenium deficiency (as well as that of zinc) may therefore reduce the amount of available T3.

      Unfortunately, dietary selenium levels have decreased significantly over the last hundred years. Moreover, it is very difficult to evaluate selenium levels in a particular individual. 33 Whenever  hypothyroidism is suspected, it is wise to increase dietary selenium. Foods that have the highest levels of selenium include Brazil nuts, sardines, turkey, beef liver and eggs, to name a few. Let's not forget that selenium is a critical trace element whose benefits include improved cardiovascular health and a reduced risk of cancer. 34 


      Zinc is a trace element that plays an important role in thyroid activity. 35 Zinc deficiency can reduce the conversion of T4 to T3 (36), thus reducing the amount of T3 available. In some cases, a simple zinc deficiency caused significant adverse effects in thyroid activity. 37 

      In a clinical report, clinicians noted that patients with alopecia (hair loss) associated with severe hypothyroidism have had very encouraging results by increasing their intake of  zinc. 38 It is very difficult to establish the need for zinc with blood tests as levels in the blood 39, as with blood levels of selenium 40, do not necessarily reflect levels in tissues. 

      Since zinc is involved in hundreds of enzyme systems in the body, adequate intake is important. Foods containing zinc include oysters, grain-fed beef, organic kefir, lamb, chickpeas, organic cocoa powder and organic pumpkin seeds. If you supplement with zinc, limit yourself to a maximum of 30 mg daily unless directed by a health-care professional.  


      The purpose of this article is to give you the information to understand the causes of hypothyroidism, a condition that is sometimes ignored and often mistreated. It is clear that the causes are many and complex. This is why it is important to consult a health care professional to help you in your approach. That said, if you have the symptoms listed in Table 1, and no other causes have  been discovered, it is very possible that hypothyroidism is involved.

      In the next article I will address the negative impact of certain foods, goitrogens, on the thyroid as well as the problem of subclinical, or tissue, hypothyroidism. This type of hypothyroidism probably affects more people than primary hypothyroidism, but as it is not easily diagnosed, thousands of people are coming back from their doctor's office without any hope of resolving their problem. Moreover, cellular hypothyroidism can even affect people who have been diagnosed with hypothyroidism and are medicated with replacement hormones such as Synthroid. In this case, the medication brings little or no real benefits, and does not seem to have a positive impact on metabolism. 

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