What is the thyroid?
The thyroid is a small butterfly shaped gland where
hormones are produced and released into the bloodstream. The major
hormones the gland makes are called T4 or thyroxine and T3 or triiodothyronine.
The production of these hormones are stimulated by another hormone
called thyroid stimulating hormone (TSH).
The thyroid hormones are very important as they control the rate
at which the body uses and stores energy from the food we eat (the metabolic
rate).
The thyroid can be found in the front of your neck
just below the Adam's apple.
What causes thyroid problems?
Thyroid problems can result from
either of the following causes:
- Overactive thyroid
If the thyroid is overactive it produces too
much T3 and T4, this condition is known as hyperthyroidism or
thyrotoxicosis.
- Underactive thyroid
If the thyroid is underactive it doesn't produce
enough T3 or T4, this condition is known as hypothyroidism ('hypo'
means under). An underactive thyroid is the most common thyroid
problem and is more common in women and people over the age of
60, though the condition can be present at birth.
What causes hyperthyroidism (overactive
thyroid)?
There are several causes of hyperthyroidism,
the most common is an autoimmune disease called Graves' disease
or diffuse toxic goitre (see below). Graves' disease occurs when antibodies , which are usually produced to fight infections stimulate the
thyroid gland into producing increased amounts of thyroid hormones.
This usually causes the thyroid gland to become enlarged, called
a goitre. Scientists are not exactly sure what causes Graves' disease
though it does tend to be an inherited condition, especially among
female members. Graves' disease may also be triggered by stress.
In the elderly a condition called toxic
nodular goitre may cause hyperthyroidism. Toxic nodular goitre occurs
when one or more small benign tumours in the thyroid gland produce excess thyroid hormones.
The thyroid gland may also become inflamed
for unknown reasons or due to a viral infection, the inflamed gland
can cause excess thyroid hormones, stored in the gland, to leak
into the bloodstream. This is usually a temporary condition and
usually clears up within 6 months, though a period of hypothyroidism
may follow before recovery is made.
What causes hypothyroidism (underacive
thyroid)?
In babies it is not known what causes
hypothyroidism. In older children and adults the most common cause
of hypothyroidism is due to the autoimmune disease, called Hashimoto's
disease, which tends to run in families. An autoimmune disease occurs
when the immune
system, which normally produces antibodies to attack foreign
substances (like viruses and other bugs), starts producing antibodies
which attack part(s) of the body. In people with hypothyroidism
the immune system attacks the thyroid cells as if they were foreign
substances.
Other possible causes may include complications
from previous thyroid surgery, treatment for previous hyperthyroidism
or certain medications, such as Lithium and Amiodarone.
Iodine and the thyroid
The thyroid gland must have iodine to
make the thyroid hormones. Iodine comes into the body in food we
eat and travels through the blood to the thyroid. Iodine is a mineral
that is found naturally in foods like seafood and milk. Iodine can
also be found in some mineral supplements that contain or are made
from kelp (a kind of seaweed), cough syrups and some medications
(Amiodarone).
A diet which is high in iodine can sometimes
cause hyperthyroidism and if you have a problem with your thyroid,
such as Graves' disease then excess iodine can make the condition
worse.
A lack of iodine in your diet can trigger
hypothyroidism. This is rare in the western world as iodine is added
to table salt, but in less developed countries iodine deficiency
is the most common cause of hypothyroidism. To the other extreme,
high intakes of iodine can occasionally prevent the thyroid gland
from working properly.
The thyroid and pregnancy
During pregnancy your immune system is
suppressed as a protection for the baby but after delivery there
is a rise in immune activity and this can trigger a thyroid disease
to develop or make a thyroid disease worse. If you or a close relative
has ever had an over or under active thyroid you should tell your
doctor when you find out you are pregnant, so that your thyroid
levels can be checked during and after pregnancy.
Hyperthyroidism or hypothyroidism is
most common in the first 2-3 months after pregnancy. However, it
will often go undetected with the normal body changes and confusion
that occurs after child birth. If pregnancy has triggered a thyroid
disease it is usually temporary and may last 3-6 months before a
full recovery is made.
The good news is most babies will be
born with completely normal thyroid function even if you developed
thyroid problems during pregnancy.
What are the symptoms of hyperthyroidism?
In hyperthyroidism the thyroid is overactive and so
the rate of metabolism speeds up, the symptoms you experience may include any of the following:
- Trouble concentrating.
- Mood swings.
- Swelling in the neck due to an enlarged thyroid
(goitre)
- Rapid or irregular heartbeat.
- Trembling hands.
- Excessive sweating.
- Insomnia - trouble sleeping.
- Weight loss in spite of increased hunger.
Women may experience irregular periods and a lighter menstrual flow. Irritated and puffy eyes is a symptom
which may be seen in people with Grave's disease. In severe cases
it can lead to excessive bulging - swelling of the eyes with a distinct
stare (caused by the upper eyelids being elevated), which in extreme
cases can cause problems with vision.
What are the symptoms of hypothyroidism?
In hypothyroidism the thyroid is underactive and so
the rate of metabolism slows down. As hypothyroidism usually develops
slowly you may have no symptoms until the condition is well advanced.
The symptoms you may have might be blamed on old age and can vary
in severity but as your metabolism continues to slow, the symptoms
should become more obvious. The symptoms may include any of the
following:
- Feeling tired and lacking energy.
- A tendency to feel the cold more than healthy
people.
- Heart may beat slower.
- Weight gain and difficulty in losing it.
- Irregular or heavy periods.
- A hoarse, croaky voice.
- Forgetfulness.
- Depression.
Later
symptoms may include constipation,
dry, pale skin and dry hair, which may be brittle and break easier.
How are thyroid problems diagnosed?
Your doctor may be able to make a diagnosis from your
history, symptoms and an examination, though a blood test should
be carried out to confirm the diagnosis. The blood tests will check
the levels of TSH (thyroid stimulating hormone), T3 and T4 in the
blood. These tests are known as thyroid function tests. If the blood
tests show levels of TSH are raised then the thyroid gland is underactive,
this is because TSH levels rise to try to manufacture more T3 and
T4. The same is true in reverse, if the thyroid is overactive and
producing above normal levels of T3 and T4 then less TSH is produced.
If inflammation of the thyroid gland is suspected,
an ultrasound scan of the gland may also be taken.
What is the treatment for hyperthyroidism?
If your doctor diagnoses you with hyperthyroidism,
the treatment you receive will depend on your age, physical condition
and the severity of the condition and may include one of the following:
- Medication - this stops or reduces the thyroid
from making too much thyroid hormone. The length of time medication
is required depends on the cause of the illness.
- Surgery - most of the thyroid is removed
and after the operation most people make a full recovery. However,
a small amount of people may then go on to develop hypothyroidism.
- Radioactive iodine - this is simple, safe
and painless, you simply take a single drink of tasteless radioactive
iodine or a capsule. This treatment is aimed at shrinking the
thyroid gland and so reducing the activity. The treatment is safe
and metabolism usually returns to normal within months.
What is the treatment for hypothyroidism?
If you have been diagnosed with hypothyroidism you
will need to take thyroxine tablets, a thyroid hormone supplement,
which simply replaces the thyroid hormone T4 which is not being
made. Occasionally you may be given T3 replacement tablets as an
alternative.
This treatment will need to be taken for life even
though you should begin to feel better. Your doctor will want to
monitor your condition with regular blood tests to check the thyroid
hormone levels and how the treatment is working.
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