Hyperthyroidism & Hypothyroidism

Hyperthyroidism is also known as an overactive thyroid and Hypothyroidism is an underactive thyroid gland. The thyroid gland is found in the neck and if it is out of balance then symptoms which range from fatigue and weight gain to hyperactvity and weight loss may be seen.

On this page:

  • Hyperthyroidism
  • Hyothyroidism



Hyperthyroidism is also known as an overactive thyroid (or sometimes thyrotoxicosis). The thyroid gland is found in the neck and is responsible for the production of the chemical thyroxine which controls energy levels. Hyperthyroidism is when too much of this chemical is produced. Read more for an explanation of this condition, the symptoms, and the treatment that can help.

What is an Overactive Thyroid Gland?

The thyroid gland is found in the neck and produces the hormone thyroxine. This hormone controls the metabolic rate which affects things like temperature and heart rate, as well as turning food into energy. An overactive thyroid produces too much of this hormone, resulting in an increased metabolism.

There are several causes of an overactive thyroid which can include Grave's disease which is an autoimmune disease where the immune system attacks the thyroid gland. Another cause can be nodules on the thyroid gland which contain abnormal thyroid tissue which affects hormone production. Taking iodine supplements can increase thyroid activity as the body uses iodine to make thyroxine. Very rarely, some medications (especially for arrhythmia) and also a thyroid cancer can increase thyroid activity.

It is also possible to have an under active thyroid (known as hypothyroidism) where not enough of the hormone thyroxine is produced. This tends to lead to fatigue, depression, and weight gain as well as other symptoms.

Symptoms of Hyperthyroidism

Here is a list of symptoms which may be present in people with hyperthyroidism. It is an extensive list and it is unlikely that any one individual would suffer all of these symptoms. However, if you experience several of these symptoms together, it is worth speaking to your Doctor.

  • Hyperactivity
  • Weight loss
  • Mood swings
  • Difficulty sleeping
  • Increased appetite
  • Fatigue
  • Reduced sex drive
  • Light or infrequent periods
  • Infertility
  • Muscle weakness
  • Needing to urinate and pass stools more frequently
  • Heat sensitivity
  • Excess sweating
  • A swelling in the neck (goitre)
  • Rapid heart rate
  • Tremors (shaking)
  • Itching skin
  • Patchy hair loss

Hyperthyroidism is diagnosed with a blood test which looks at the levels of thyroxine and also the thyroid stimulating hormone (TSH).


Treatment of an overactive thyroid aims to return the levels of thyroxine production to normal.

In mild cases (with few or even no symptoms) your Doctor may decide not to provide any treatment initially and instead to monitor your condition via regular blood tests. In many cases, the hormone levels will return to normal on their own.

In more moderate to severe cases, you will be referred for specialist treatment. This may include options such as:

Thionamides (carbimazole and propylthiouracil) are medications which reduce the production of thyroxine. You will need to take this form of medication for at least 6-8 weeks before you start to notice a difference.

Once your hormone production has stabilized then your Doctor may gradually reduce your dosage.

Rare side-effects include nausea, a skin rash, achy joints, and itchy skin. In some very rare cases, Thionamides have been known to cause a condition called agranulocytosis which is a sudden drop in white blood cells. This is a serious condition as it lowers the bodies immune system. If you notice any symptoms of fever, a sore throat, mouth ulcers or any other signs of infections, visit your Doctor immediately.

Beta Blockers are sometimes prescribed whilst your thyroid is brought back under control. These can help to reduce some of the symptoms such as a tremor and hyperactivity.

Radioiodine treatment is a form of radiotherapy which can be used to treat most types of hyperthyroidism. It works by shrinking the thyroid so that it produces fewer hormones.

Surgery is sometimes performed in severe cases to remove part or all of the thyroid gland. This is known as a partial or full thyroidectomy. It is important that the right amount of the thyroid gland is removed as taking away too much can result in an underactive thyroid!

This is a permanent treatment option and is used on those whose thyroid has swollen and is causing neck problems.


Hypothyroidism is also known as an underactive thyroid gland. The thyroid gland is found in the neck and produces the hormone thyroxine which controls how much energy your body is using. Hypothyroidism is when the gland doesn't produce enough of this hormone. This condition is most common in women and is normally caused when the immune system attacks the thyroid gland.

What is an Underactive Thyroid?

The thyroid gland is found in the neck and produces the hormone thyroxine. An underactive thyroid does not produce enough of this hormone, which causes many of the body's functions to slow down. It is also possible to have an overactive thyroid (hyperthyroidism), where too much thyroxine is produced, resulting in the bodily functions speeding up. The symptoms are usually quite the opposite of an underactive thyroid.

Hypothyroidism can affect both men and women, although it is far more common in women.

An underactive thyroid is usually caused by an autoimmune response where the immune system starts to attack the thyroid gland. This causes damage to the gland and a reduction in hormone production. There are a few other causes, although these are quite rare. Treatment for an overactive thyroid can sometimes be too effective and result in too little thyroxine being produced. Other rare causes include a lack of iodine, viral infections, other medications and pituitary gland problems. Congenital hypothyroidism is a form found in babies. All newborns are screened for this using a small sample of blood about a week after birth.

Having an underactive thyroid is not usually a serious condition and it can be treated with medications. An underactive thyroid cannot be prevented.

Symptoms of Hypothyroidism

Symptoms of an overactive thyroid gland tend to develop very gradually over a period of a few years. For this reason, it is often difficult to detect them and symptoms are often overlooked by both the Doctor and patient.

The most common symptoms include:

  • Fatigue
  • Weight gain
  • Aching muscles
  • Depression
  • Dry skin and hair
  • Always feeling cold
  • Constipation
  • Heavy, irregular periods in females

The only way to determine if you have hypothyroidism is via a blood test which can be taken at your Doctors surgery. This shows the levels of hormones in the blood.


Treatment of hypothyroidism is usually achieved via a hormone replacement medication known as Levothyroxine. This medication replaces the thyroxine hormone which your body is not producing naturally.

The dose you are given depends on the results of your blood tests. In many cases, a low dose is prescribed initially and then regular blood tests are taken and the dose increased as necessary.

Levothyroxine does not have any side effects as it is simply the hormone which your body is missing. Some people find that their symptoms improve almost straight away, although with some it may take a few weeks or months.