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HYPOTHYROIDISM
UNDERACTIVE
THYROID
 What is an underactive thyroid (hypothyroidism)?
 How does it develop?
 What can I do to help control my hypothyroidism?
Information for people with, or at high risk of, hypothyroidism
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?
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:
öö Tiredness
öö Excessive sleepiness
öö Weight gain
öö Constipation
öö Feeling depressed
öö Being sensitive to the cold
öö Irregular menstrual periods
öö History of infertility
Most cases of underactive thyroid are caused by:
öö Dry skin and hair
öö 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)
öö Hair thinning or loss
öö 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)
öö Difficulty concentrating, and forgetting things
öö Thyroid damage resulting from some treatments
used for overactive thyroid, or thyroid cancer
(including surgical removal of the thyroid gland)
öö 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
öö Side-effects of some drugs used to treat other
conditions, such as some cancer drugs
öö 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
öö Hoarse voice
öö Goitre (swelling of the neck)
öö Muscle aches or cramps
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:
öö Thyroid function tests: a small sample of your
blood is tested to measure TSH and sometimes T4
öö 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:
öö A high level of TSH and a low level of T4  this could
mean you have an underactive thyroid
öö 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
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.

Take your drug at the right time
- for example, some thyroxine treatments should be
taken once a day, on an empty stomach with water
Your doctor, nurse and
pharmacist can help you
to achieve your treatment
goals
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.
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.org
American 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:
EXCEMED - Excellence in Medical
Education is an independent, non-profit
continuing medical education (CME)
provider based in Geneva, Switzerland.
The Foundation has delivered top CME to
thousands of healthcare professionals for
over four decades, convening over 1500
international scientific congresses with
over 500 proceedings published in leading
international medical journals. EXCEMED
has pioneered online CME courses since
2000 and offers e-learning activities
including video lectures, CME-accredited
online courses and symposia.
www.excemed.org
All EXCEMED programmes are organised solely
to promote the exchange and dissemination
of scientific and medical information. No forms
of promotional activities are permitted.
This programme is made possible thanks
to an educational grant received from Merck.
Source materials
NHS UK Underactive thyroid (hypothyroidism) fact sheet. Available at: www.nhs.uk/conditions/thyroid-under-active/pages/introduction.aspx
Thyroid Function Tests. Available at: http://labtestsonline.org.uk/understanding/analytes/thyroid-function/tab/glance
Thyroid UK: www.thyroiduk.org.uk/tuk/about_the_thyroid/hypothyroidism.html