Underactive thyroid (hypothyroidism)

When to see your GP

Symptoms of an underactive thyroid are often similar to those of other conditions, and they usually develop slowly, so you may not notice them for years.

You should see your GP and ask to be tested for an underactive thyroid if you have symptoms including:

• tiredness
• weight gain
• depression
• being sensitive to the cold
• dry skin and hair
• muscle aches

The only accurate way of finding out whether you have a thyroid problem is to have a thyroid function test, where a sample of blood is tested to measure your hormone levels.

Read more about testing for an underactive thyroid.

Who's affected

Both men and women can have an underactive thyroid, although it's more common in women. Children can also develop an underactive thyroid and some babies are born with it.

All babies born in the UK are screened for congenital hypothyroidism using a blood spot test when the baby is about 5 days old.

Treatment for an underactive thyroid involves taking daily hormone replacement tablets, called levothyroxine, to raise your thyroxine levels.

You'll initially have regular blood tests until the correct dose of levothyroxine is reached. This can take a little while to get right.

Once you're taking the correct dose, you'll usually have a blood test once a year to monitor your hormone levels.

You'll usually need treatment for the rest of your life. However, with proper treatment, you should be able to lead a normal, healthy life.

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).

Many of the body's functions slow down when the thyroid does not produce enough of these hormones.