The Highs & Lows of Thyroid Function

An underactive thyroid can be difficult to detect even though it brings a wide range of symptoms, some mild, others debilitating. It is, however, possible to make a sure diagnosis if the complex pattern of cause and effect between hypothyroidism and its symptoms are understood.

The butterfly-shaped thyroid gland weighs between 8g and 40g and lies at the front of your neck, across your wind-pipe, between your breastbone and Adam’s apple. It has a wide range of functions.

It controls metabolism, promotes cell growth and assists in elimination of your waste through lymph. It directly controls oxygen turnover in every cell in your body, regulates your temperature and helps control your hormone function. Your hormones direct nearly every system or process in the body, so a whole range of symptoms can be experienced when the thyroid gland is not functioning properly.

If your blood tests for thyroid function are normal but you continue to experience symptoms, you may have a more subtle form of hypothyroidism known as euthyroid sick syndrome (ESS), low T3 syndrome, non-thyroidal illness (NTI), functional hypothyroidism or subclinical hypothyroidism.

What’s interesting is that patients with high (hyperthyroidism) or low (hypothyroidism) thyroid function can complain of the same symptoms – fatigue, brain fog, hair loss, insomnia, heart palpitations, irritable bowel, muscle weakness and menstrual irregularities. The patterns of cause and effect between hypothyroidism and its symptoms are complex. Probably the most debilitating symptom of all is the deep-seated tiredness experienced as the result of slowing down of all body systems and organs. This constant fatigue can leave you depressed and anxious.

The Highs & Lows of Thyroid Function


The ‘old’ way of thinking about hypothyroidism was ‘all about the gland’, without considering its context in the body as a whole. For example, mainstream medical thinking identifies the following primary causes of hypothyroidism:

  • congenital (born without a thyroid), called congenital cretinism
  • abnormal metabolic defect of the thyroid
  • auto-immune thyroiditis (where the gland is attacked by its own immune system), called Graves’ disease or Von Basedow’s disease (if the gland is over-active), or Hashimoto’s disease (if the gland is underactive)
  • over-treated hyperthyroidism, e.g. by surgical removal of part of the gland or with the use of radioactive iodine
  • many drugs reduce the level of, or inhibit the activity of the thyroid
  • certain cancers
  • viral infection
  • pituitary insufficiency.

The new way of thinking, in the paradigm of Functional Medicine, is more along the lines of ‘at what level is there a problem?’ It recognises that the presenting symptoms may have many layers of causes. The thyroid gland can be inefficient or exhausted without being damaged or diseased. This mild dysfunction can be identified and addressed through suitable nutrition and supplementation.

The Highs & Lows of Thyroid Function

The Highs & Lows of Thyroid Function

If you are experiencing the majority of these symptoms, you may have an underactive thyroid gland (hypothyroidism).


There is a good deal of controversy surrounding testing for low thyroid function. In his address at the 14th International Symposium of Functional Medicine (May 2007),1 Dr Alan B. McDaniel stated that in many cases blood tests for thyroid do not reveal what is wrong with you. A blood test is not always a reliable indication of functional hypothyroidism. A blood test will detect levels of hormones being transported in the blood at one particular moment, and not what the body is producing over time.

Medical practitioners often rely on the thyroid-stimulating hormone (TSH) reading as the primary diagnosis for low thyroid function. There is no doubt that TSH is integral to thyroid function. TSH is affected by many factors. Stress, lack of sleep and high serum cholesterol can increase TSH levels. Ageing, depression, anxiety and fasting can decrease them. The function of the hypothalamus, circadian rhythm, seasonal variations and changes in pulse rate all impact on TSH levels. A more complete strategy to assess thyroid function would include testing of all hormones produced by the thyroid gland – free T3, free T4, TSH, reverse T3 and total T3.

A useful screening test for thyroid function, developed by Dr Broda Barnes, is to take your morning temperature over a period of time. A temperature consistently lower than 36.6 degrees Celsius indicates that your thyroid is not functioning optimally and requires further assessment. In my practice I use the 24-hour urine functional test to assess tissue levels of T3 produced over a full day.


In order to treat the thyroid it is important to understand how it works and what it needs to function optimally. The thyroid gland is regulated by a part of the brain called the hypothalamus, and the pituitary gland. As if operated by a thermostat, these glands release hormones that regulate thyroid hormone production depending on what the body requires. If the hypothalamus and pituitary are not communicating effectively, thyroid hormone output will be compromised.

The thyroid gland works by producing hormones, chemical messengers that go out into the body and exert various effects on their target cells. TSH released by the pituitary gland will stimulate or inhibit production of the thyroid hormone, thyroxine (T4), in the thyroid gland. The thyroid gland requires very specific nutrients to be able to make thyroid hormones – iodine, L-tyrosine, iron, manganese, vitamin A, vitamin B1, vitamin C and vitamin E. Without these nutrients, thyroid hormones cannot be produced adequately.


Limit goitrogens, foods known to reduce thyroid activity. These include the cruciferous plants such as kale, cabbage, cauliflower, swede, mustard, turnip, rape, horseradish and Brussels sprouts, and foods such as soya, cassava, maize, millet, peanuts, almonds, walnuts, pine nuts, carnitine and quercitin.

Include nutrients required as building blocks for thyroid hormone production. These include tyrosine, an amino acid that can be found in avocados, pumpkin seeds, cashew nuts, bananas and dairy products, and iodine, a mineral abundant in all products from the sea, especially algae (kelp), marine iodised salt, shellfish and sea fish (sardines), but also found in foods such as radishes, onions, mushrooms, turnips, pineapple and egg whites.

Include the co-factors needed for the enzyme 5’-deiodinase to form the active thyroid hormone T3 from T4. These are:

  • Zinc, found in red meat, liver, fish, egg yolks, oysters
  • Selenium, found in Brazil nuts, garlic, onions, egg yolks, wheat germ, tuna, kale, tomato, broccoli, shellfish Copper, found in shellfish (shrimps), seafood (oysters), plums, liver, nuts, avocado, mushrooms, potatoes, green leafy vegetables and cocoa
  • Vitamin E, found in unrefined oils (cold pressed), whole grains, wheat germ, milk, egg yolk, green leafy vegetables, lettuce, avocado, nuts, seeds, nut butter.

Ensure adequate intake of nutrients required for healthy thyroid function.

  • Iron: Lean meats, liver, apricots, eggs, kidneys, whole grains, molasses, eggs, shellfish, dried fruits
  • Manganese: Whole grains, wheat germ, seeds, leafy vegetables, brewer’s yeast, egg, liver, onions, green beans, parsley, strawberries, bananas, apples, pineapple, cherries
  • Vitamin A: Milk, butter, cheese, yoghurt, egg yolk, liver, kidneys, sweetbreads, fatty fish, fish liver oil
  • Vitamin B1: Whole grains, nuts, dried beans, peas, lentils, liver, kidney, pork, brewer’s yeast, wheat germ, eggs.
  • Vitamin C: Fruit and vegetables, sprouts, watercress.

Assess whether the following factors are inhibiting thyroid function:

Toxic metals such as cadmium, lead and mercury
Stress, infection (fever), chronic illness, severe dieting, a low-protein diet, carbohydrate withdrawal.


Numerous causes including lifestyle, psychological factors, stress, environmental factors, poor diet and lack of nutrients, pregnancy, immunity, and poor detoxification should all be considered in the diagnosis and treatment of any reader presenting with symptoms of hypothyroidism.

Editor's Note:


This condition is often misdiagnosed as it shares the same symptoms as classic low thyroid symptoms. WTS is characterised by a sub-normal body temperature and patients usually have normal thyroid levels. It can be treated with herbal combinations or cycles of slow-release hormone T3. Refer to the article Wilson’s Temperature Syndrome by Dr David Nye in, click here:

Improve Health Wilson’s Temperature Syndrome


1. McDaniel AB. Thyroid assessment: controversies and conundrums [CD-R] (2007).14th International Symposium of Functional Medicine, Institute for Functional Medicine, USA.

Further reading

    1. Durrant-Peatfield B. The Great Thyroid Scandal and How to Survive It. London: Baron’s Down Publishing, 2003.
    2. Holford P., and Burne J. Food Is Better Medicine Than Drugs. London: Piatkus, 2008.
    3. McDaniel AB. Thyroid Assessment: Controversies and Conundrums (CD-R) (2007). 14th International Symposium of Functional Medicine, Institute for Functional Medicine, USA.
    4. Mouton G. BCNH: Functional Hormonology. London: British College of Nutrition and Health, 2003.
    5. Mudd M. Why Am I So Tired? Is Your Thyroid Making You Ill? London: Thorsons, 2000.
continue to top