Information for people with, or at high risk of, hypothyroidism

How does it develop? What is an underactive thyroid (hypothyroidism)?

What can I do to help control my hypothyroidism?

HYPOTHYROIDISMUNDERACTIVE THYROID

WHAT IS THE THYROID?

The thyroid is a gland at the front of your neck. It produces hormones (chemical substances) that travel through the bloodstream and control how your body functions and uses energy (that is, your metabolism). The thyroid also controls growth in early life, even before birth.

The hormones produced by the thyroid are thyroxine (also known as T4) and tri-iodothyronine (T3).

WHAT IS HYPOTHYROIDISM?

An underactive thyroid (hypothyroidism) is when your thyroid gland doesn't produce enough of the thyroid hormones (T4 and T3) to meet your body’s needs.

Hypothyroidism affects almost all of the organs in the body because thyroid hormones are important for ensuring normal function of essentially all of the cells in the body.

For example, hypothyroidism can slow down the metabolism of fat and cause high cholesterol levels, which may lead in the long term to an increased risk of clogging of the arteries (called atherosclerosis), and an increased risk of heart attacks.

WHAT CAUSES HYPOTHYROIDISM?Most cases of underactive thyroid are caused by:

A lack of dietary iodine: iodine is needed to make thyroid hormones. Worldwide, this is the most common cause of hypothyroidism but is easily corrected if iodine is added to salt (this happens in many countries)

The immune system attacking, and damaging, the thyroid (this is called an autoimmune reaction). Hashimoto’s disease is the most common type of autoimmune reaction. This is the most common cause of hypothyroidism in countries where iodine deficiency is not a problem (that is, in countries where iodine is routinely added to salt)

Thyroid damage resulting from some treatments used for overactive thyroid, or thyroid cancer (including surgical removal of the thyroid gland)

In fetuses, lack of development of the thyroid gland, or deficiencies in some enzymes (which are proteins that are important for thyroid hormone synthesis); this is called congenital hypothyroidism

Side-effects of some drugs used to treat other conditions, such as some cancer drugs

A problem with the pituitary gland, which is a gland below the brain that regulates the thyroid by producing thyroid-stimulating hormone (TSH). This is also described as secondary hypothyroidism

HOW COMMON IS HYPOTHYROIDISM?Worldwide, about 5% of people have hypothyroidism. Prevalence increases with age and hypothyroidism is much more common in women than men.

WHAT ARE THE SYMPTOMS OF HYPOTHYROIDISM?The symptoms of hypothyroidism are not that specific; in other words, they overlap with many symptoms that people experience. For example, fatigue, constipation and weight gain are common in people who do not have any underlying illness, but these also often occur in people with hypothyroidism.

Common symptoms of an underactive thyroid are often similar to common symptoms of other conditions, so it is always important to see your doctor if you have several of the following symptoms:

Tiredness Excessive sleepiness Weight gain Constipation Feeling depressed Being sensitive to the cold Irregular menstrual periods History of infertility Dry skin and hair Hair thinning or loss Hoarse voice Goitre (swelling of the neck) Muscle aches or cramps Difficulty concentrating, and forgetting things

The more symptoms you have, the more likely that you may have hypothyroidism, but your doctor will run a few tests to confirm if this is the case.

WHAT HAPPENS IF I HAVE SYMPTOMS OF HYPOTHYROIDISM?

Your doctor might want you to have some tests, such as:

Thyroid function tests: a small sample of your blood is tested to measure TSH and sometimes T4

Thyroid antibodies: a small sample of your blood might be tested to look for indications of autoimmune thyroid disease (e.g. Hashimoto’s disease)

WHAT DO THE NUMBERS MEAN?Thyroid function tests help to determine if you have hypothyroidism, and also the type of hypothyroidism that you have. Therefore, blood tests might show:

A high level of TSH and a low level of T4 this could mean you have an underactive thyroid

Normal or low TSH and low T4 this could suggest that you may have an underactive thyroid because there is a problem with your pituitary gland (secondary hypothyroidism)

HOW OFTEN SHOULD I HAVE THYROID FUNCTION TESTS?

If you have been diagnosed with hypothyroidism and you have started treatment, at first your doctor will check your levels of TSH regularly (by asking you to go for blood tests every 4–6 weeks). This is to check that you are receiving the right dose of drug (i.e. the level that keeps your TSH in the normal range).

Once you’ve reached the correct dose for you, your treatment will continue and your doctor will probably arrange for you to have blood tests once or twice a year.

WHAT CAN BE DONE TO INCREASE THYROID HORMONE LEVELS?

If your T4 levels are clearly low and your doctor diagnoses you with hypothyroidism, he/she may prescribe a thyroxine preparation that replaces the T4 that your body should be producing. Your doctor will increase the dose of treatment gradually until you feel well again and your T4 levels return to normal.

There are also many things that you can do to improve your thyroid health and your response to thyroid treatment. These include:

Stop tobacco use- smoking affects the thyroid

Avoid taking other drugs at the same time as thyroxine

- check with your doctor or pharmacist if you have to stop your other drugs or if you should take them

at a different time

Take your drug at the right time

- for example, some thyroxine treatments should be taken once a day, on an empty stomach with water

CAN I HAVE A NORMAL LIFE IF I HAVE HYPOTHYROIDISM?

Yes, you can have an absolutely normal life in all aspects if you take the right doses of thyroxine – and you take it regularly.

Hypothyroidism is a lifelong disease that is usually managed by your family physician, although you might be referred to a specialist (an endocrinologist) if you experience any problems or you become pregnant. It’s also important to tell your family that you have hypothyroidism because thyroid disease can run in families. If other members of your family have, or develop, some of the common symptoms of thyroid disease described earlier in this leaflet, they should ask their own doctors whether thyroid function tests might be needed.

Your doctor, nurse and pharmacist can help you to achieve your treatment

goals

Source materialsNHS UK Underactive thyroid (hypothyroidism) fact sheet. Available at: www.nhs.uk/conditions/thyroid-under-active/pages/introduction.aspxThyroid Function Tests. Available at: http://labtestsonline.org.uk/understanding/analytes/thyroid-function/tab/glanceThyroid UK: www.thyroiduk.org.uk/tuk/about_the_thyroid/hypothyroidism.html

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WHERE CAN I GET MORE INFORMATION ON HYPOTHYROIDISM?If you have any questions, ask your doctor, nurse or pharmacist. Your clinic will also be aware of any local groups that offer support to people with (or at high risk of) hypothyroidism.You could also visit the following websites*:British Thyroid Foundation: www.btf-thyroid.orgAmerican Thyroid Association: www.thyroid.org Iodine Global Network: http://ign.org

*Websites often contain information that is specific to the country in which they were written (e.g. USA, UK). Ask your doctor about local websites that provide information that is directly relevant for you.

Here are the details of your local clinic: