Hyperthyroidism 101: Symptoms, Causes, Diagnosis & Treatment

Learn all about hyperthyroidism including its symptoms, causes, risk factors, treatment, diet & medications.

by Nathasha Lee

Thyroid disorders are estimated by medical experts to affect between 5 to 10 percent of Singapore’s population. One of these conditions is hyperthyroidism, which results when our thyroid glands are over-active and causes our body’s metabolism to increase very quickly. This leads to consequences like irregular heartbeat and unexpected weight loss. In this article we will explain what hyperthyroidism is, how it is diagnosed and treated, and what you can do to manage the effects of hyperthyroidism.

What is Hyperthyroidism?

The thyroid is a butterfly-shaped endocrine gland located in the neck that secretes hormones named thyroxine and triiodothyronine into the bloodstream. These hormones are responsible for regulating the cells and tissues in our body so that they can work properly. Thyroxine is secreted to organs like the liver and kidneys where it plays a role in normal heart function, digestion, brain development, muscle control and bone health.

Hyperthyroidism is when your thyroid produces too much thyroxine for your body’s needs. This causes the activity of the body cells to increase to an abnormal amount, which has wide-ranging effects on many systems in the body. Hyperthyroidism is more common in women than in men. It generally occurs in adults aged between 20 to 40 years of age.

Hyperthyroidism vs Hypothyroidism

The names of these two thyroid conditions might be similar, but hyperthyroidism and hypothyroidism have different causes. Hyperthyroidism is caused by an over-active thyroid gland but conversely, hypothyroidism occurs when the thyroid gland is less active than normal. This causes organs in the body to work less well, causing one’s metabolism to slow down. Symptoms of hypothyroidism can also be different from hyperthyroidism because of their divergent effects on organ systems. Hypothyroidism is characterised by constipation caused by decreased bowel activity, slower heart rate.

Hypothyroidism is generally more common than hyperthyroidism. In studies conducted with sample populations from the US, hyperthyroidism was found in 0.8 per cent of the population compared to hypothyroidism which affected around 3.7% of the population.

Hyperthyroidism Symptoms

Some symptoms of hyperthyroidism include:

  • Sudden weight loss despite no changes in one’s diet or appetite.
  • Difficulties sleeping
  • Persistent tiredness
  • Intolerance to heat
  • Excessive sweating
  • Fast and irregular heartbeat
  • Increased bowel movements
  • Increased blood sugar. Hyperthyroidism speeds up the rate at which insulin, the hormone that regulates our blood sugar is absorbed. This can make controlling blood sugar more difficult especially for those with diabetes. 
  • Anxiety
  • Sore and gritty eyes
  • Tremor in the arms and legs
  • Swelling in the neck, known as a goiter. This is caused by thyrotoxicosis, which happens when you have an enlarged thyroid gland.  
  • Irregular menstruation

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Hyperthyroidism Causes

Below are some of the common causes of hyperthyroidism:

Irregular Hormone Production by the Thyroid

Irregular hormone production by the thyroid can be caused by autoimmune disorders, where the body’s immune system attacks the thyroid cells. One of the most common causes of hyperthyroidism is Graves’ disease, an autoimmune disorder that targets the thyroid and makes it produce more hormones than usual. Lumps may also grow on your thyroid that may increase the production of thyroxine in a condition known as thyroiditis. Painless or silent thyroiditis happens when the thyroid tissue is being destroyed by the body’s cells and causes excessive levels of thyroid hormone to be released into the bloodstream.

Toxic Adenoma

Another common cause is toxic adenoma. Also commonly known as Plummer’s disease, it occurs from mutations in hormone receptors or genes in a thyroid nodule. These nodules start to produce too much thyroid hormones, leading to hyperthyroidism.


Childbirth can sometimes trigger thyroid disorders in a condition known as postpartum thyroiditis. This happens when the thyroid becomes inflamed within the first year after giving birth. While scientists are not exactly sure what causes postpartum thyroiditis, you are more likely to get it if you have had antithyroid antibiotics before pregnancy or type 1 diabetes. It is usually temporary and will go away anywhere between a few weeks to several months after childbirth.

Hyperthyroidism Risk Factors

People with autoimmune disorders will have a higher chance of being affected by hyperthyroidism. If you have conditions like rheumatoid arthritis (a disorder that causes swelling in one’s joints), celiac disease (a digestive disorder which causes an inability to digest gluten) or type 1 diabetes you will have a higher chance of getting Graves’ disease which is a leading cause of hyperthyroidism.

If your family members have a history of autoimmune disorders, you will have a higher chance of getting hyperthyroidism yourself. A 2011 study found that family members of people with autoimmune thyroid conditions are 15 to 16 times more likely to be diagnosed with similar conditions themselves.

You might also be at risk of hyperthyroidism if you have an iodine-rich diet. Our bodies require iodine to produce thyroid hormones, and too much or too little iodine can impact our thyroid health. Iodine can be found in foods like seaweed, table salt, sea fish like tuna and cod, and shellfish. Some medicines for heart disease also contain iodine. If you are taking iodine dietary supplements, try to keep them under 0.5mg a day.

Complications of Hyperthyroidism

If you face many symptoms of hyperthyroidism, please see your doctor to treat the condition early before more serious complications arise. Hyperthyroidism that is left for long without treatment can cause lasting damage to your heart. Consequences include an abnormal heartbeat, congestive heart failure, and even cardiac arrest.

Hyperthyroidism can also affect your eyes and skin. Problems like decreased range of eye movement, ulcers on the cornea which makes the eye unable to close properly, and loss of vision can happen as a result of prolonged eye symptoms caused by Graves’ disease. The increased metabolic rate caused by hyperthyroidism can lead to problems with the skin and nails such as distorted nails which lift off the nail bed (onycholysis), generalised itching, thinned scalp hair.

When left untreated, hyperthyroidism can also cause more serious chronic conditions like osteoporosis and premature menopause. The body will begin to pull nutrients from the bones when increased metabolism causes the body to consume nutrients quickly, causing one’s bone density to decrease and leading to osteoporosis in the future.  

Hyperthyroidism Diagnosis

You can seek specialised diagnosis and treatment by booking an appointment with specialists at the endocrinology department you can find in hospitals. A blood test is generally used to first detect signs of thyroid disease. Hyperthyroidism can be diagnosed by measuring the levels of thyroid-stimulating hormone (TSH) in the bloodstream. Regular TSH levels range between 0.4 and 4.0 mU/L. Hyperthyroidism is characterised by lower TSH levels in the bloodstream than normal and higher levels of thyroxine and triiodothyronine.

Other tests may be carried out such as a physical examination to check for unusual lumps in the neck and an analysis of your medical history and symptoms. An ultrasound may also be used to check for deformities in the thyroid.

Hyperthyroidism Treatment

Hyperthyroidism can be treated using medication that stops your thyroid from producing too much thyroxine.


Carbimazole and propylthiouracil are some of the main hyperthyroidism medications used. It may take around one to two months before you notice any effects of the medication. However, depending on the severity of your condition you may have to continue taking the medication for several months or even for life to control your thyroid’s hormone production.

Beta blockers, which are medications that slow down heart rate, might be prescribed to quickly control cardiac symptoms of hyperthyroidism like an irregular heartbeat. You might have to see your doctor to adjust your medication dosage if your body produces too much or too little thyroid hormone. Avoid taking beta blockers if you have conditions like low blood pressure, asthma, lung disease, or have had severe allergic reactions to medication in the past.


This can also be used where a procedure known as radioiodine treatment is used to destroy cells in the thyroid and decrease its function so that it does not produce an excessive quantity of hormones. While this can reduce symptoms within three to six months, it can also cause thyroid activity to slow down and lead to hypothyroidism. Repeated exposure to radiation may also increase your risk of developing cancer. You should speak to your doctor if you are concerned about your cancer risk. You should not go for radioiodine therapy if you are pregnant or breastfeeding as the radioactive iodine can pass from mother to child in the womb or through breast milk.


In cases where your thyroid can no longer carry out regular hormone production, you may have to undergo surgery to remove part of or the whole of your thyroid gland. You will need to meet with a specialist to discuss appropriate treatment options for your condition. Suitable treatment options would be different for each person based on factors like age, effects of medicine taken for other conditions, and other conditions like pregnancy or heart disease.

Hyperthyroidism Diet

You might need to make changes to your diet to prevent the over-production of thyroid hormones. Below we will introduce some foods to avoid and others that we can recommend that can help control your hyperthyroidism.

Foods to include


Broccoli and other cruciferous vegetables like cabbage, cauliflower and spinach naturally prevent the production of thyroid hormones. Adding more cruciferous vegetables to your regular diet can prevent the over-production of thyroxine.

Dairy Products

Your body will use up its stores of calcium more quickly when you have hyperthyroidism since it speeds up the body’s metabolism. Dairy products are rich in calcium and can help you to maintain healthy bones and teeth. Adding some milk, yoghurt or cheese to your diet can help prevent the loss of bone density that is a common complication of hyperthyroidism.


Egg yolks are an accessible and affordable food source which contain vitamin D. The body needs vitamin D to promote calcium absorption, which helps in maintaining healthy bones, and to regulate other processes like cell growth. Other foods that contain vitamin D include liver, cheese, and mushrooms. Your body also naturally produces vitamin D from exposure to sunlight.

Foods to avoid

Caffeinated Drinks

Beverages containing caffeine increase one’s heart rate and blood pressure, which might worsen symptoms of hypertension like tremors in the hands and rapid heartbeat. Avoid drinking coffee and black tea.

Refined Sugar

Foods with refined sugar release sugar quickly into the bloodstream. As hyperthyroidism affects the body’s ability to regulate blood sugar, eating foods high in refined sugar can make it harder for you to control your blood sugar levels.

Soy Products

Soybeans contain chemicals which encourage the production of thyroid-stimulating hormone and could worsen existing hyperthyroidism symptoms. A 2015 study found that consuming soya was associated with higher TSH levels. As such it is recommended that people with hyperthyroidism limit their consumption of soy products like tofu, soy milk and tempeh.


Now that you learn about hyperthyroidism, and its treatment and diet, we should steer clear from its possible triggers to avoid complications and serious health risks.

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About the Writer
Nathasha Lee
Nathasha Lee is a final-year Anthropology major at Yale-NUS College. She hopes her writing can make a positive difference in the lives of readers, no matter how small. In her spare time, she enjoys making art, listening to podcasts, and drinking lots of tea.
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