Hyperthyroidism

Hyperthyroidism

Understanding Hyperthyroidism

Hyperthyroidism is a condition where the thyroid gland works more than it should do. It can result in a number of different signs and symptoms that we have discussed here.

Symptoms of hyperthyroidism

The thyroid gland is responsible for maintaining the function of a number of different vital structures in the body. In addition, it has a role to play in the smooth running of the normal metabolic and physiological processes in the body.

Excessive release of thyroid hormone that is seen in hyperthyroidism leads to overactivity of a number of different systems in the body.

General features – Weight loss despite having a normal or increased appetite is a classic feature.

Brain – Hyperthyroidism can lead to excitability, nervousness, anxiety and lack of sleep. Fine tremors of the hands can be seen as well.

Heart– Increased heart rate, irregular heart rhythms (called atrial fibrillation) and occasional breathlessness

Skin – Excessive sweating, thinning of the skin

Muscles – Weakness of the muscles and fatigue

Eyes – In Grave’s disease, the enlargement of tissues behind the eye lead to ‘popping’ out of the eyeballs.

Others – Menstrual cycles can become excessive and irregular. Increased frequency of bowel motions can occur, though diarrhoea itself is uncommon.

It is not uncommon for the initial symptoms of hyperthyroidism to be ignored. Many tend to put down the symptoms to stress or anxiety. As time passes, the weight loss and fatigue becomes severe and concerning. Some may look upon this as a good thing for their health, but the weight loss is actually an unhealthy weight loss as opposed to what is achieved through dieting.

Causes of Hyperthyroidism

Almost 7 out of 10 cases of hyperthyroidism are due to overproduction of thyroid hormone in a condition called Grave’s disease. Grave’s disease is an autoimmune condition that occurs due to the development of antibodies against the thyroid gland. In other words, the body’s immunity starts to act against the thyroid gland itself.

Grave’s disease can be hereditary and is common in young women. Noticeable swelling or lumps are seen in the thyroid gland that can be felt by the treating physician and seen on imaging studies.

Sometimes however, there can be multiple lumps in the thyroid gland. This is called multi-nodular goitre or toxic nodular goitre.

A viral infection can sometimes lead to inflammation of the thyroid gland, making it overactive. This is called thyroiditis.  Excessive intake of prescribed thyroid hormone tablets for underactive thyroid disease can also cause symptoms of an overactive thyroid.

Diagnosis of hyperthyroidism

A diagnosis of hyperthyroidism can be made initially from clinical history alone. On examination, a goitre may be felt in the neck. The presence of excessive sweating, eye protrusion, tremors in the hand and overactive muscle reflexes all point towards this problem.

Laboratory tests are very useful in making a diagnosis. A simple blood test that assesses the levels of thyroid stimulating hormone, T4 levels and T3 levels can confirm a diagnosis. In hyperthyroidism, the TSH levels are very low, while the T4 and T3 levels are elevated.

If blood tests show the thyroid is overactive, then additional scans can be done. These can help differentiate between toxic nodular changes or thyroiditis.

Thyroid uptake scans may also be performed if needed.

Treatment of Hyperthyroidism

There are a number of different factors that dictate treatment in hyperthyroidism. Background medical problems, age and the severity of the condition are some of the prime factors.

If a diagnosis of hyperthyroidism has been made by a physician, it is a good idea to consult with an endocrinologist who deals with these medical problems on a regular basis.

(i) Antithyroid drugs

Antithyroid drugs are agents that prevent the thyroid gland from producing excessive amounts of the thyroid hormone. The most commonly used drug is methimazole, though in rare cases propylthiouracil may also be used. The former is preferred due to its lower side effect profile.

Antithyroid drugs are fast acting and can bring thyroid hormone levels under control safely and effectively. The usual course of treatment is around 12 to 18 months, which results in remission in around 30% of patients with Grave’s disease.

However, these drugs may be used as a bridge to radioactive iodine therapy as well.

Antithyroid drugs have a low side effect profile, causing allergic reactions in only 5 out of 100 cases. Other minor side effects include a skin rash, hives and joint pains.

Very rarely (in about 1 in 500 cases), the white blood cell count may reduce. White blood cells are responsible for maintaining a defence system against infections. If the white blood cell count reaches zero, it is called agranulocytosis. This can be a life threatening problem as the lack of these cells can lead to the person developing serious infections.

If agranulocytosis has occurred, stopping the drug can revert the blood count back to normal. Continuing the drug has harmful effects.

Propylthiouracil (PTU) can lead to liver side effects and symptoms such as jaundice and abdominal pain. It is however rarely used these days.

(ii) Radioactive iodine

This form of treatment is effective in managing an overactive thyroid gland. Iodine is the essential element needed for the synthesis of thyroid hormone. When producing the hormone, iodine is take up by the thyroid gland.

If radioactive iodine is administered to the patient, the gland will take this up as well. It destroys the overactive thyroid cells thus helping bring the thyroid hormone levels to below normal.

Radioactive iodine is administered in the form of a tablet. Once it has done its job, any excess radioactive iodine is removed from the body.

Thyroid hormone levels take a few weeks to improve, and concurrently the size of the thyroid gland will reduce as well. If the levels only reduce partly and the patient remains in a hyperthyroid state, a further dose may be administered.

Usually, treatment with radioactive iodine makes the thyroid gland underactive. This means that the patient will have to take thyroid supplements for the remainder of their life. This treatment is completely harmless and very effective.

Radioactive iodine therapy is safe in both patient above 60 years and children above the age of 5 years. There has been no clear indication that the risk of thyroid cancer increases.

(iii) Surgery

Surgical removal of the thyroid gland is another way to treat hyperthyroidism. Prior to surgery however, medical therapy will be prescribed to bring the degree of hyperthyroidism to an acceptable level.

Once surgery has been planned, the surgeon may ask the patient to take a non-radioactive iodine supplement called Lugol’s iodine (super-saturated potassium iodide). This reduces the quantity of blood reaching the thyroid gland, making it smaller and making it easier for the surgeon to remove.

Surgical treatment is safe in the hands of an experienced surgeon. However there is a 1% risk of complications such as damage to the nearby parathyroid glands and nerves that supply the vocal cord.

Removal of the thyroid gland will make you hypothyroid. Thyroid supplementation will be needed.

(iv) Beta Blockers

As previously mentioned, excessive amount of the thyroid hormone can cause anxiety, increased heart rate and tremors. These symptoms can be easily controlled with the use of drugs called beta blockers.

The commonly used drug is propranolol, though newer agents such as atenolol, metoprolol and nadolol are also being used these days.

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