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.

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 to 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.