Hyperthyroidism – Over Active Thyroid Function

The thyroid gland regulates many aspects of our metabolism and affects many bodily processes including how many calories we burn, how warm we feel and how much we weigh.

In healthy people, the thyroid is stimulated by thyroid stimulating hormone (TSH) to make just the right amounts of two hormones, T4 and T3, which have important actions throughout the body. 

These hormones also have direct effects on most organs, including the heart which beats faster and harder under the influence of thyroid hormones. Essentially all cells in the body will respond to increases in thyroid hormone with an increase in the rate at which they conduct their processes.

Hyperthyroidism is the medical term used to describe the signs and symptoms associated with an overproduction of thyroid hormones.

The thyroid hormones can be tested to see if they are out of balance and if you have hyperthyroidism. 


Although there are several different causes of hyperthyroidism, most of the symptoms that patients experience are the same regardless of the cause. These include:

  • Feeling hot /heat intolerance
  • Weight loss
  • Increased appetite
  • Difficulty sleeping despite feeling tired
  • Trembling hands
  • Irregular heartbeat
  • Irritability
  • Nervousness
  • Feeling very emotional 
  • Light or absent menstrual periods
  • Hair loss
  • Staring gaze
  • Diarrhoea

In severe cases sufferers may experience:

  • Shortness of breath
  • Chest pain
  • Muscle weakness

If you suffer from these symptoms it’s advisable to have a thyroid blood test to measure thyroid hormone levels and check for markers that indicate the underlying cause of the thyroid dysfunction.

Contributory factors

Graves’ disease: the most common underlying cause of hyperthyroidism is Graves’ disease. It’s characterised by an enlarged thyroid gland, also called a goitre, which produces too much thyroid hormone.

The disease itself is classified as an autoimmune disease because it’s caused by the body’s own immune system attacking the thyroid gland. The antibodies produced by the immune system then attach to specific activating sites on thyroid gland which in turn cause the thyroid to make more hormone.

Most Graves’ symptoms are isolated to those caused by the over active thyroid. However, in some cases inflammation of the tissues around the eyes and thickening of the skin over the lower legs can also occur. This can cause eye irritation, a staring gaze or, in extreme cases, bulging of the eyes, severe inflammation, double vision or blurred vision.

Graves’ disease effects women much more often than men and typically occurs in the 30s and 40s. It also tends to run in families.

Oxidative damage: oxidative damage is caused by unstable molecules called free radicals which can damage the body’s cells and DNA. Free radicals occur in the environment around us as well as being made during normal, healthy bodily processes. Normally the body has very good mechanisms for mopping them up before they do us any damage, but constant exposure to high levels can overwhelm our body’s defence mechanism.

In hyperthyroidism all the processes inside the body are running much faster than normal, so many more free radicals are produced. If the hyperthyroidism is also accompanied by inflammation, such as in thyroiditis, the free radical load becomes even higher.

Monitoring and controlling oxidative damage is therefore an important preventative step in hyperthyroidism therapy. An Oxidative Stress Test indicates how much oxidative stress your body is under – and how well your defence mechanisms are working.

Thyroid nodule: hyperthyroidism can also be caused by single benign (non-cancerous) lumps or tumours in the gland called nodules which sometimes produce excessive amounts of thyroid hormones.

Nodules are comprised of thyroid cells which have lost the regulatory mechanism which dictates how much hormone to produce. Without this regulatory control, the cells produce thyroid hormone at a dramatically increased rate causing the symptoms of hyperthyroidism.

Inflammation of the thyroid gland: this is called thyroiditis and can lead to the release of excess amounts of thyroid hormones that are normally stored in the gland.

Some cases are triggered by a virus and usually only last a few weeks. A more common painless form of thyroiditis occurs in 1 out of 20 women, a few months after having a baby and is, therefore, known as postpartum thyroiditis.

Excessive thyroid medication: hyperthyroidism can also occur in patients who take excessive doses of any of the available forms of thyroid hormone.

Contributory factors

Diet: nutrition can play an important role in helping to control thyroid function. Certain foods, called goitregens, can help to slow down an overactive thyroid by limiting the amount of hormones the gland is able to make. High levels of essential fatty acids can also slow thyroid function and reduce inflammation in cases of thyroiditis. Other more stimulating dietary factors such as caffeine can have the opposite effect, markedly exacerbating the condition.

If you have hyperthyroidism, Smart Nutrition can assess your current diet, helping you to reduce stimulants and increase thyroid-tempering foods. Please use the button at the bottom of the page to find out more.

Food sensitivities: hyperthyroidism may be caused or exacerbated by food sensitivities that are delayed in expressing their effects in the body. Common culprits are dairy products and gluten-containing grains, although sensitivities to other foods and drinks may also be present.

A Food Intolerance Test provides an excellent solution to this problem by identifying trigger foods. 

Malabsorption: a common symptom of hyperthyroidism is an increased transit time, often characterised by diarrhoea. This means the body has much less time to extract the nutrients for food which can lead to nutritional deficiencies and increased weight loss. Digestive upset can also interfere with the delicate balance of bacteria in the gut which can have an impact on immune function.

If you have loose stools and you’re confident that your thyroid medication is regularly checked and in balance, it’s worth investigating whether you have any digestive imbalances with a Comprehensive Stool Test.

Useful Links

Please do not return samples to the laboratories that may arrive after Wednesday 27th March and up to and including Monday 2nd April.

The laboratories are closed from the 28th March – 2nd April for the Easter Holiday.