The thyroid gland
The thyroid gland is a small butterfly-shaped gland in the neck, just in front of the windpipe (trachea).
One of its main functions is to produce hormones that help regulate the body’s metabolism (the process that turns food into energy). These hormones are called triiodothyronine (T3) and thyroxine (T4).
When the thyroid does not produce enough thyroxine, many of the body’s functions slow down.
An underactive thyroid, also called hypothyroidism, means your thyroid gland does not produce enough chemicals called thyroid hormones.
Common signs of an underactive thyroid are tiredness, weight gain and feeling depressed.
An underactive thyroid is not usually serious. It can often be treated successfully by taking daily hormone tablets to replace the hormones your thyroid isn’t making.
An underactive thyroid cannot be prevented. Most cases are caused either by your immune system attacking your thyroid or by damage to your thyroid that can occur during some treatments for thyroid cancer and an overactive thyroid.
Read more about the causes of hypothyroidism.
When to see a doctor?
Symptoms of hypothyroidism are often confused for something else by patients and doctors and they develop slowly so you may not notice them for years.
You should see your doctor and ask to be tested for hypothyroidism if you have symptoms including:
being sensitive to the cold
dry skin and hair
The only accurate way to find out if you have a thyroid problem is to have a blood test to measure your hormone levels.
Read more about the symptoms of hypothyroidism and testing for hypothyroidism.
Who is affected
Both men and women can have an underactive thyroid, although it’s more common in women. Around 1 in 3,500-4,000 babies is born with an underactive thyroid (called congenital hypothyroidism). Newborn babies can be screened for congenital hypothyroidism using a heel-prick blood test when the baby is about five days old.
Treatment for an underactive thyroid involves taking daily hormone-replacement tablets, called levothyroxine, to raise your thyroxine levels. You will usually need treatment for the rest of your life. However, with proper treatment you should be able to lead a normal, healthy life.
If it’s not treated, an underactive thyroid can lead to complications, including heart disease, goitre (a lump in the throat caused by a swollen thyroid), pregnancy problems and a life-threatening condition called myxoedema coma (although this is very rare).
The thyroid gland