Hyperthyroidism

What is hyperthyroidism?

Hyperthyroidism is a condition in which the levels of thyroid hormones in the blood are increased and is characterised by a metabolic imbalance. The thyroid gland is a small endocrine gland located at the base of the neck. It produces thyroid hormone, which control various body functions. Hyperthyroidism or thyrotoxicosis results from excess quantities of thyroid hormone in the body.

What are the causes?

There are several causes of hyperthyroidism:

• Graves’ disease is the most common cause and occurs when the immune system produces antibodies that activate and stimulate the thyroid gland, and results in production of hormones in large amounts.
  
• Thyroiditis, or the inflammation of the thyroid gland, can sometimes lead to excess amounts of thyroid hormone.
  
• Hyperthyroidism can occur in patients who take an over-dose of any of the available forms of thyroid hormone.
  
• Certain benign or cancerous tumours can also result in increased secretion of thyroid hormone.
  
• Some forms of goitres or thyroid enlargements can result in hyperthyroidism.

What are the symptoms?

There are various symptoms of hyperthyroidism which may be present differently in different individuals:

• Weight loss
  
• Increased appetite
  
• Anxiety, nervousness and restlessness
  
• Heat intolerance
  
• Increased sweating
  
• Fatigue
  
• Muscle cramps
  
• Irregular menstrual periods in women
  
• Goitre or thyroid enlargement
• Palpitations and rapid heart rate
• Protruding eyes
  
• Excessive thirst
  
• Sleep disturbances
  
• Skin colour changes and itching
  
• Nausea and vomiting
  
• Uncoordinated movement
  
• Tremors
  
• Breast development in men
  
• High blood pressure
  
• Hair loss
  

How is it diagnosed?

The diagnosis of hyperthyroidism is based on physical examination and laboratory tests. Physical examination may also detect thyroid enlargement or goitre. Laboratory tests include blood tests such as measurement of serum TSH (thyroid stimulating hormone), T3 and T4. In some cases, the test to detect antithyroid antibodies may also be useful. A nuclear imaging scan called a thyroid uptake scan, measures how well the thyroid is functioning. This can help diagnose the specific cause of hyperthyroidism. Iodine thyroid scan will show if the cause is a single nodule or the whole gland. X-rays may also be used to diagnose the problem.

What is the treatment?

The main aim of the treatment is to reduce the production of thyroid hormone. This can be done with the help of drugs such as propylthiouracil, methimazole and potassium iodide. Medications called beta-blockers, including atenolol or metoprolol, can also be used to block the effects of thyroid on tissues and to treat symptoms like rapid heart rate, tremors, palpitations, sweating, and anxiety.

Radioactive iodine is the most widely recommended permanent treatment of hyperthyroidism. A radioactive form of iodine is given which gives off radiation which destroy the thyroid cells that preferentially absorb them.

Surgery is another permanent treatment of hyperthyroidism, which may include partial or complete removal of the gland.