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Underactive thyroid - What will happen to me?

BMJ Group Medical Reference

If your underactive thyroid is treated, you should be able to lead a normal, active life. But if it's not treated, your symptoms may gradually get worse.

If you have symptoms

If your underactive thyroid isn't treated, your symptoms may get gradually worse.

You may not be able to think as clearly or as fast. You may get depressed, put on weight, or become constipated, or your skin may become very dry. Your voice could get hoarse. If you are a woman, your periods may become irregular. This could affect whether you can get pregnant.

An underactive thyroid can also make your heart beat more slowly and your cholesterol level rise.[10] Although researchers aren't certain, both of these things may put you at risk of getting heart disease.

Very occasionally, an underactive thyroid can cause a more serious illness that needs treating in hospital.[11] These illnesses include:

If you don't have symptoms

If you have the mild form of this condition and don't get any symptoms, you could go on to get the more serious form in time. Each year between 2 in 100 and 4 in 100 women with mild hypothyroidism go on to get symptoms.[12] The risk is much higher in men.[12]

You may also be more likely to get heart disease, although researchers aren't yet sure. One study found that people with a mildly underactive thyroid had higher levels of cholesterol in their blood.[10]

Another study showed that older women with a mildly underactive thyroid were more likely to have a heart attack and to have fatty deposits in the blood vessels of their heart.[13]

But we're not sure whether getting treatment for a slightly underactive thyroid gland reduces your risk of heart disease. Some research shows it may help your heart to work better.[14]



Cholesterol is a fat-like substance made by your liver or absorbed from food. It is used by your body to make bile acids (which help your intestines absorb nutrients) and steroid hormones (like testosterone or oestrogen). Cholesterol is also an important part of cell membranes, which are the structures that surround cells. 'Good cholesterol' is called HDL; 'bad cholesterol' is LDL.


When you're constipated, you have difficulty passing stools (faeces). Your bowel movements may be dry and hard. You may have fewer bowel movements than usual, and it may be a strain when you try to go.


Dementia is when your brain stops working properly. Someone with dementia may become gradually more confused and forgetful. A common cause of dementia is Alzheimer's disease.

heart disease

You get heart disease when your heart isn't able to pump blood as well as it should. This can happen for a variety of reasons.

For more terms related to Underactive thyroid


For references related to Underactive thyroid click here.
Last Updated: June 21, 2012
This information does not replace medical advice.  If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.
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