Covers hypothyroidism, which happens when the thyroid doesn't make enough thyroxine (T4) and triiodothyronine (T3) hormones. Includes causes like thyroiditis. Covers tests for TSH, T4, and T3. Also includes info on treatment with medicine such as levothyroxine.
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This topic provides
information about hypothyroidism. Hypothyroidism means your thyroid is not
making enough thyroid hormone. If you are looking for information about when
the thyroid makes too much thyroid hormone, see the topic
What is hypothyroidism?
Hypothyroidism means your
thyroid is not making enough
thyroid hormone. The thyroid is a butterfly-shaped
gland in the front of your neck. It makes hormones that control the way your
body uses energy.
Having a low level of thyroid hormone affects your
whole body. It can make you feel tired and weak. If hypothyroidism is not
treated, it can raise your
cholesterol levels. During pregnancy, untreated hypothyroidism can
harm your baby. But hypothyroidism can be treated with medicine that can help you feel like yourself again.
of any age can get hypothyroidism, but older adults are more likely to get it.
Women age 60 and older have the highest risk. You are more likely to get the
disease if it runs in your family.
What causes hypothyroidism?
In the United States,
the most common cause is
Hashimoto's thyroiditis. It causes the body's
immune system to attack thyroid tissue. As a result,
the gland can't make enough thyroid hormone.
Other things that
can lead to low levels of thyroid hormone include surgery to remove the thyroid
gland and radiation therapy for cancer. Less common causes include viral
infections and some drugs, such as amiodarone and lithium.
What are the symptoms?
Hypothyroidism can cause
many different symptoms, such as:
Feeling tired, weak, or
Dry skin and brittle nails.
Not being able
to stand the cold.
Memory problems or
having trouble thinking clearly.
Symptoms occur slowly over time. At first you might not
notice them, or you might mistake them for normal aging. See your doctor if you
have symptoms like these that get worse or won't go away.
How is hypothyroidism diagnosed?
Your doctor will
ask questions about your symptoms. You will also have a physical exam. If your
doctor thinks you have hypothyroidism, a simple blood test can show if your
thyroid hormone level is too low.
How is it treated?
Doctors usually prescribe pills to treat hypothyroidism. Most people start to feel better
in a week or two. Your symptoms will probably go away within a few months.
But you will likely need to keep taking the pills from now on.
It's important to take your medicine just the way your doctor
tells you to. You will also need to see your doctor for follow-up visits to
make sure you have the right dose. Getting too much or too little thyroid
hormone can cause problems.
If you have mild hypothyroidism, you
may not need treatment now. But you'll want to watch closely for signs that it
is getting worse.
If you are diagnosed with severe
hypothyroidism, you will need to be treated right away in the hospital. Severe
hypothyroidism can lead to a rare but dangerous disease called
Should you get tested for hypothyroidism?
important to watch for signs of the disease so it can be treated promptly.
These signs may be easy to miss, so testing is a good idea for:
In the United States, the most common
Hashimoto's thyroiditis. This is a condition that causes the
body's natural defenses—the immune system—to produce
antibodies that over time destroy thyroid tissue. As a
result, the thyroid gland cannot make enough
deficiency is the number one cause of hypothyroidism. But iodine added to salt,
food, and water has nearly eliminated this problem in the U.S. and other
Other common causes of hypothyroidism
Thyroid surgery. Part or all of the thyroid
gland may be removed to treat disorders such as having too much thyroid hormone
(hyperthyroidism), an enlarged thyroid gland (goiter) that makes swallowing difficult, thyroid
thyroid nodules that may be overactive or cancerous.
Hypothyroidism results when the thyroid gland is removed or when remaining
thyroid tissue does not function properly.
therapy, which is often used to treat hyperthyroidism. Radioactive iodine
therapy can destroy the thyroid gland, leading to
External beam radiation, which is used to treat
some cancers, such as
Hodgkin's lymphoma. This radiation treatment can
destroy the thyroid gland.
Less common causes include:
Infections. Viral and bacterial infections can
temporarily damage the thyroid gland. This causes a short-term form of the
condition. Hypothyroidism caused by infection usually does not result in
Medicines. Some medicines can interfere
with normal production of thyroid hormone. Lithium is one of the most
common medicines that causes hypothyroidism. Others include amiodarone (such as
Cordarone or Pacerone) and interferon alfa (such as Intron A or Roferon A).
In rare cases, disorders of the
pituitary gland or the
hypothalamus (secondary and tertiary forms of
hypothyroidism). The pituitary gland and hypothalamus produce hormones that
control the thyroid and, as a result, affect its ability to produce thyroid
Excessive iodine, which, in food or medicines, can reduce
the function of the thyroid gland. This is usually
Congenital hypothyroidism. In rare cases, an infant is
born without a properly functioning thyroid gland. All children born in a
hospital in the U.S. are tested at birth for hypothyroidism.
hypothyroidism usually appear slowly over months or
years. Symptoms and signs may include:
Coarse and thinning hair.
A yellowish tint to the
Slow body movements.
Inability to tolerate cold.
sluggish, or weak.
depression, or problems
Heavy or irregular
menstrual periods that may last longer than 5 to 7
Swelling of the arms, hands, legs, and feet, and facial
puffiness, particularly around the
Muscle aches and cramps.
In general, how bad your symptoms are depends on your age,
how long you have had hypothyroidism, and the seriousness of the condition. The
symptoms may be so mild and happen so slowly that they go unnoticed for years.
Symptoms of hypothyroidism during
and after pregnancy include fatigue, weight loss, dizziness, depression, and
memory and concentration problems.
Because of the range of symptoms, hypothyroidism can be mistaken for
depression, especially during and after pregnancy. In older people, it may be
dementia, and other conditions that cause memory
Symptoms of hypothyroidism in infants, children, and teens
Although rare, hypothyroidism can occur in
infants, children, and teens. In infants, symptoms of
a goiter include a poor appetite and choking on food. Symptoms of
hypothyroidism may include dry, scaly skin. In children and teens, symptoms
include behavior problems and changes in school performance. Children and teens
may gain weight and yet have a slowed growth rate. Teens may have delayed
puberty and look much younger than their age.
hypothyroidism may get better or worse over time,
depending on its cause and your age.
Hypothyroidism in infants and children
rare, hypothyroidism can occur in
infants and children. If hypothyroidism is treated
within the first month of life, a child will grow and develop normally.
Untreated hypothyroidism in infants can cause brain damage, leading to
intellectual disability and
developmental delays. In the United States, all
children are tested for hypothyroidism at birth.
Intellectual disability usually does not occur if hypothyroidism develops
after age 3. But untreated childhood hypothyroidism typically delays physical
growth and sexual development, including the onset of
puberty. Children may gain weight yet have a slowed
Hypothyroidism in adults
Hypothyroidism caused by
Hashimoto's thyroiditis sometimes will disappear on
its own. More often, the disorder causes a gradual loss of thyroid function. Your symptoms may develop slowly and be so mild that you do not notice them for
years. But symptoms usually grow worse. And health problems may develop as the
If untreated, hypothyroidism may lead
Myxedema, a condition that causes swelling of
tissues, increased fluid around the heart and lungs, slowed muscle reflexes,
and a slowed ability to think.
a rare, life-threatening condition. This can occur if you have had
hypothyroidism for many years that becomes markedly worse. It usually occurs
when older adults who have severe hypothyroidism become ill with another
condition, suffer from cold exposure, or take painkillers or sleeping pills.
Symptoms include mental deterioration, such as apathy, confusion, and
psychosis. You may lose consciousness (coma) and may
have an extremely low body temperature (hypothermia), slow heartbeat (fewer
than 60 beats per minute),
heart failure, and trouble
Complications, such as:
Increased levels of
triglycerides (increasing the risk of
coronary artery disease and
Fluid around the heart (pericardial effusion).
Sleep apnea, which causes you to stop breathing for 10
seconds or longer while sleeping.
People with mild (subclinical) hypothyroidism
have only slightly
abnormal thyroid blood test results and often do not have obvious symptoms or
health problems. Some people who have mild hypothyroidism regain normal thyroid
function. But about 1 out of 10 people who have mild hypothyroidism will go on to have hypothyroidism within 3 years.1
thyroid gland has been removed during surgery,
hypothyroidism will occur within a few weeks. If you have been treated with
radioactive iodine therapy, hypothyroidism may develop within a year. In these cases, thyroid function typically does not return,
and you will need to take thyroid hormone medicine from now on.
Hypothyroidism during and after pregnancy
who have hypothyroidism or mild hypothyroidism before they become pregnant may
have more severe hypothyroidism during their pregnancy. If not treated,
pregnant women who have hypothyroidism can develop
preeclampsia and have a premature delivery. Children
born to women who have untreated hypothyroidism during pregnancy are at risk for
having hypothyroidism at birth and low birth weight and may score lower on
intelligence tests than children of healthy mothers.2
After delivery, women may have a thyroid
disorder called postpartum thyroiditis. This condition occurs in about 5% of
women who do not have a history of thyroid disease.2
It is often mistaken for
Women who have postpartum
thyroiditis often develop hypothyroidism 3 to 6 months after delivery. The
hypothyroidism may last up to several months. It sometimes occurs after an initial episode of postpartum
thyroiditis that causes symptoms from too much thyroid hormone. Hypothyroidism may become permanent in
women with postpartum thyroiditis. Even if thyroid gland function returns to normal, postpartum
thyroiditis usually comes back during later pregnancies.
What Increases Your Risk
Many things may increase
your risk for hypothyroidism. These include:
Age and being female. Older
adults are more likely to develop hypothyroidism than younger people. And women
are more likely than men to develop thyroid disease.
Previous thyroid problems. Thyroid disease, an enlarged thyroid (goiter), and surgery or radiation therapy to treat
thyroid problems increase the likelihood of having hypothyroidism in the
Some lifelong conditions. Type 1 diabetes, vitiligo (an
autoimmune disease that causes patches of light skin),
pernicious anemia, and leukotrichia (premature gray hair) are seen more often in people who have
Iodine deficiency. This is
rare in the United States but common in areas where iodine is not added to
salt, food, and water.
medicines can interfere with normal thyroid function, particularly lithium, amiodarone (such as
Cordarone or Pacerone), and interferon alfa (such as Intron A or Roferon A).
When To Call a Doctor
Call 911 or other emergency services immediately if you or a person you know has
hypothyroidism and has signs of
myxedema coma, such as:
Mental deterioration, such as apathy,
Extreme weakness and fatigue
that progress to loss of consciousness (coma).
difficulties, slow heart rate (less than 60 beats per minute), or low body
temperature [95°F (35°C) or
See your doctor if you have any symptoms that don't go
Feeling tired, sluggish, or
depression, or difficulty
An inability to tolerate cold.
brittle nails, or a yellowish tint to the
Heavy or irregular
menstrual periods that may last longer than 5 to 7
If you have one or two of the above symptoms that have not
changed or have changed very little over a long period of time, it is less
likely that the symptoms are caused by hypothyroidism. Consult your doctor.
Talk to a doctor if you are pregnant and have some
of the above symptoms. Also talk to a doctor if you have hypothyroidism and are
pregnant or are trying to become pregnant. Your dose of thyroid hormone
medicine may need to be changed.
Watchful waiting—a period of time during which
you and your doctor observe your symptoms or condition without using medical
treatment—is not appropriate for hypothyroidism that is causing symptoms.
Treatment should begin as soon as the condition is diagnosed.
Watchful waiting may be appropriate for certain adults with
mild (subclinical) hypothyroidism whose blood tests
show only modest changes. Talk to your doctor about treatment, its cost and
possible risks and benefits. Watch for any signs that you may be getting
hypothyroidism. Doctors often want people to have yearly thyroid
function blood tests to check to see if
thyroid hormone production is normal.
medical history and
physical exam are the first steps in diagnosing
mild (subclinical) hypothyroidism. If the results lead
your doctor to suspect you have hypothyroidism or subclinical hypothyroidism,
you will have tests to confirm the diagnosis.
Blood tests are
always used to confirm a diagnosis of hypothyroidism or mild hypothyroidism.
The tests used most often are:
Because of the possibility of
intellectual disability in infants with hypothyroidism,
every state in the United States tests newborns for hypothyroidism. If your
baby was not born in a hospital, or if you believe your baby may not have been
tested, talk to your doctor. Screening tests for hypothyroidism
are not always accurate. Even if test results show no problem, watch your child for
symptoms of hypothyroidism, such as poor appetite, not gaining weight, and dry skin.
Some doctors now recommend routine testing for people at
risk for hypothyroidism, including:
People age 35 and older. The American Thyroid
Association guidelines recommend that screening begin at age 35 and continue
every 5 years thereafter.3
People with one
or more close relatives who have or had hypothyroidism.
with conditions associated with
Hashimoto's thyroiditis, including
pernicious anemia, and
type 1 diabetes.
Pregnant women. In
pregnant women known to have hypothyroidism, tests should be done at regular
intervals to determine whether the dosage of thyroid hormone medicine is
Women who are having symptoms of hypothyroidism after
pregnancy (postpartum hypothyroidism), such as
depression, memory and concentration problems, or
thyroid enlargement (goiter). Women
who have had hypothyroidism during or after pregnancy should be retested if
they become pregnant again.
Not all experts agree on whether to recommend widespread
screening for hypothyroidism. Some groups say there is not enough evidence of
benefit to recommend screening for everyone. But people who are at high
risk—women older than 60 and anyone with a family history of thyroid disease or
who has other
autoimmune diseases—may want to be screened.4
can be easily treated using thyroid hormone medicine. The most effective and
reliable thyroid replacement hormone is man-made (synthetic). After starting
treatment, you will have regular visits with your doctor to make sure you have
the right dose of medicine.
In most cases, symptoms of
hypothyroidism start to improve within the first week after you start
treatment. All symptoms usually disappear within a few months. Infants and
children with hypothyroidism should always be treated. Older adults and people
who are in poor health may take longer to respond to the medicine.
If you have had radiation therapy and have
hypothyroidism, or if your
thyroid gland has been removed, you will most likely
need treatment from now on. If your hypothyroidism is caused by
Hashimoto's thyroiditis, you might also need treatment
from now on. Sometimes, thyroid gland function returns on its
own in Hashimoto's thyroiditis.
If a serious illness or infection
triggered your hypothyroidism, your thyroid function most likely will return to
normal when you recover.
Some medicines may cause hypothyroidism.
Your thyroid function may return to normal when you stop the
If you have
mild (subclinical) hypothyroidism, you may not need
treatment but should be watched for signs of hypothyroidism getting worse. You and your doctor will talk about the pros and cons of taking medicine to treat your mild hypothyroidism. The dose of
thyroid medicine must be watched carefully in people who also have heart disease,
because too much medicine increases the risk of chest pain (angina) and
irregular heartbeats (atrial fibrillation).
Your doctor will treat your
hypothyroidism with the thyroid medicine levothyroxine (for example, Levothroid, Levoxyl, or Synthroid). Take your medicine as
directed. You will have another blood test 6 to 8 weeks later to make sure the
dose is right for you.
If you take too little medicine, you may
have symptoms of hypothyroidism, such as constipation, feeling cold or
sluggish, and gaining weight. Too much medicine can cause nervousness,
problems sleeping, and shaking (tremors). If you have heart disease, too much
medicine can cause irregular heartbeats and chest pain. People who also have heart
disease often start on a low dose of levothyroxine, which is increased
If you have severe hypothyroidism by the time you are
diagnosed, you will need immediate treatment. Severe, untreated hypothyroidism
myxedema coma, a rare, life-threatening condition.
Treatment during pregnancy is especially important, because hypothyroidism
can harm the developing fetus.
If you develop hypothyroidism during
pregnancy, treatment should be started immediately. If you have hypothyroidism
before you become pregnant, your thyroid hormone levels need to be checked to make sure that you have the right dose of thyroid medicine. During pregnancy,
your dose of medicine may need to be increased by 25% to 50%.5
If you develop
hypothyroidism after pregnancy (postpartum hypothyroidism), you also may need treatment. You will be
retested for hypothyroidism if you become pregnant again. In some cases
hypothyroidism will go away on its own. In other cases it is permanent and
requires lifelong treatment.
You are likely to need treatment
hypothyroidism from now on. As a result,
you need to take your medicine as directed. For some people, hypothyroidism gets worse as they age and the dosage of thyroid medicine may have to be
increased gradually as the thyroid continues to slow down.
people treated with thyroid hormone develop symptoms again if their medicine is
stopped. If this occurs, medicine needs to be restarted.
serious illness or infection triggers your hypothyroidism, your thyroid
function most likely will return to normal when you recover. To check
whether thyroid function has returned to normal, thyroid hormone medicine may
be stopped for a short time. In most people, a brief period of hypothyroidism
occurs after thyroid medicine is stopped. There is often a delay in the body's
signals that tell the thyroid to start working again. If the thyroid can
produce enough hormone on its own, treatment is no longer needed. But if
hormone levels remain too low, you need to restart thyroid medicine.
While taking thyroid hormone medicine, you need to see your doctor once a
year for checkups. You will have a blood test (thyroid-stimulating hormone [TSH] test) to make sure you have a normal hormone
Treatment if the condition gets worse
hypothyroidism continue, such as sluggishness,
constipation, confusion, and feeling cold. This may occur if you are not taking
enough thyroid hormone or if your medicine is not absorbed from your
gastrointestinal tract. Having a bowel disease or taking certain other
medicines may block thyroid hormone. If needed,
your doctor will increase your dose.
Your doctor may
suggest you try the combination therapy of
T3/T4 medicine if T4 medicine is not controlling your
If your dose of thyroid hormone is too high, you may
develop complications such as irregular heartbeats and, over time,
osteoporosis. If you have heart disease, too much
medicine can cause pain (angina) and irregular heartbeats. Your doctor will
watch your thyroid levels using a
thyroid-stimulating hormone (TSH) test. If needed,
your doctor will lower your dose.
Most cases of
hypothyroidism in the United States are caused by
Hashimoto's thyroiditis, which cannot be
Although you can't prevent hypothyroidism, you can
watch for signs of the disease so it can be treated promptly. Some people who
are at high risk for having hypothyroidism but do not have symptoms can be
tested to see whether they have mild, or subclinical, hypothyroidism.
Expert groups differ in their recommendations for screening. For example:
The American Thyroid Association recommends
that all adults be tested beginning at age 35 and continuing every 5
years.3 Older adults, especially women older than 60,
those with a
family history of hypothyroidism, and those who have
pernicious anemia, or
type 1 diabetes should also be tested, according to
U.S. Preventive Services Task Force makes no
recommendation for or against thyroid screening for people who do not have
symptoms of hypothyroidism. The USPSTF states there is not enough
evidence to support screening.4
panel of experts from several medical specialties recommends against widespread
screening.6 But these health professionals say that if
you are high risk, you may want to be screened. Those at high risk include
women older than age 60 and people who have type 1 diabetes or other
autoimmune diseases.6 Talk to
your doctor about whether you should be screened.
If you have
hypothyroidism, see your doctor once a year so your
condition can be closely checked and your treatment adjusted, if needed.
Be sure to take thyroid hormone medicine correctly. Talk
with your doctor if you don't understand the reason for taking medicine
regularly or if you think you have any side effects from the medicine. You
usually need to have regular blood tests to find out whether you are receiving
the correct amount of thyroid hormone.
Children who have
hypothyroidism also need to see a doctor regularly, because the amount of
thyroid hormone medicine they need changes as they grow. Untreated
hypothyroidism in infants and very young children can have severe consequences.
As soon as you think your child is able to understand (usually around age 9 or 10), teach him or her about
hypothyroidism, the importance of taking medicine correctly, and why regular
health checkups are important.
Some health food stores in the
United States sell "natural" forms of thyroid hormone. The quality and
effectiveness of these natural agents are unregulated. Some may not work at
all. Others may have an active ingredient that does work but that may be
dangerous to certain people.
Reduces or eliminates symptoms of
hypothyroidism. Symptoms usually improve within the first week after you begin
therapy. All symptoms usually disappear within a few months.
reduce the risk of slowed physical growth,
intellectual disability, and behavioral problems in infants
Thyroid hormone medicine does not cause side effects if you
take the correct dose.
What to think about
People who have hypothyroidism
need treatment with thyroid hormone medicine. Depending on the cause of their
hypothyroidism, they may need treatment for the rest of their lives.
Taking certain supplements, such as calcium or iron (or both), at the
same time as thyroid hormone medicine may reduce the amount of thyroid hormone
medicine absorbed by the body. Take calcium supplements at least 4 hours before
or after taking thyroid hormone medicine. Also avoid
taking iron supplements at the same time as thyroid medicine.
to your doctor about whether you need to change your dose of thyroid medicine
if you also take birth control pills or other hormones. You may need to take
more thyroid hormone medicine than you would if you were not taking these
Follow-up visits with your
doctor are important to make sure that you are taking the correct dose of
medicine. Most people have blood tests 6 to 8 weeks after
starting treatment. After thyroid hormone levels return to normal, thyroid
function tests are typically rechecked once a year.
Other Places To Get Help
American Thyroid Association
6066 Leesburg Pike
Falls Church, VA 22041
1-800-THYROID (1-800-849-7643) (703) 998-8890
The American Thyroid Association promotes scientific and public
understanding of thyroid disorders. It publishes a monthly journal and manages
a Web site.
National Endocrine and Metabolic Diseases Information Service (NEMDIS) (U.S.)
6 Information Way
Bethesda, MD 20892–3569
The National Endocrine and Metabolic Diseases Information Service
is a service of the National Institute of Diabetes and Digestive and Kidney
Diseases, National Institutes of Health. This Web site offers consumer
information on the cause, treatment, and effects of endocrine and metabolic diseases.
How this information was developed to help you make better health decisions.