Home > Health Library > Hypothyroidism
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
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.
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.
Hypothyroidism can cause
many different symptoms, such as:
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.
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.
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
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:
Learning about hypothyroidism:
Living with hypothyroidism:
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
Less common causes include:
hypothyroidism usually appear slowly over months or
years. Symptoms and signs may include:
Some less common symptoms may include:
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.
Mild (subclinical) hypothyroidism often causes no
symptoms or vague symptoms that may be attributed to aging, such as memory
problems, dry skin, and fatigue.
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
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.
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 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
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.
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.
Many things may increase
your risk for hypothyroidism. These include:
Call 911 or other emergency services immediately if you or a person you know has
hypothyroidism and has signs of
myxedema coma, such as:
See your doctor if you have any symptoms that don't go
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.
Hypothyroidism can be diagnosed by a:
Hypothyroidism also may be diagnosed by a specialist,
such as a
psychiatrist, depending on the symptoms you have and
who you see to evaluate the symptoms.
Complicated or unusual cases
of hypothyroidism may require consultation with an
To prepare for your appointment, see the topic Making the Most of Your Appointment.
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:
If the above tests are not normal, antithyroid antibody tests may determine whether you
have the autoimmune disease
Hashimoto's thyroiditis, in which the body's defense
system attacks the thyroid gland.
In rare cases, a thyroid ultrasound may be used to evaluate a
thyroid gland that during a physical exam seems to be abnormal.
computed tomography (CT) scan or
magnetic resonance imaging (MRI) of the hypothalamus
or pituitary gland may be done to look for any changes in these areas of the
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:
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.
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.
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
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:
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.
Thyroid hormone medicine is the only
effective way to treat
hypothyroidism. In most cases, thyroid hormone
Thyroid hormone medicine does not cause side effects if you
take the correct dose.
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.
The American Thyroid Association promotes scientific and public
understanding of thyroid disorders. It publishes a monthly journal and manages
a Web site.
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.
Hueston WJ (2011). Hypothyroidism. In ET Bope et al., eds., Conn's Current Therapy 2011, pp.
678–680. Philadelphia: Saunders.
American College of Obstetricians and Gynecologists
(2002, reaffirmed 2010). Thyroid disease in pregnancy. ACOG Practice Bulletin
No. 37. Obstetrics and Gynecology, 100(2):
Ladenson PW, et al. (2000). American Thyroid
Association guidelines for detection of thyroid dysfunction. Archives of Internal Medicine, 160:
U.S. Preventive Services Task Force (2004). Screening
for thyroid disease: Recommendation statement. Annals of Internal Medicine, 140: 125–141.
Brent GA, Davies TF. (2011). Hypothyroidism and thyroiditis. In S Melmed et al., eds., Williams Textbook of Endocrinology, 12th ed., pp. 406–439. Philadelphia: Saunders.
Surks MI, et al. (2004). Subclinical thyroid disease:
Scientific review and guidelines for diagnosis and management. JAMA, 291(2): 228–238.
Other Works Consulted
Cooper DS, Ladenson PW (2011). The thyroid gland. In DG Gardner, D Shoback, eds., Greenspan's Basic and Clinical Endocrinology, 9th ed., pp. 163–226. New York: McGraw-Hill.
Drugs for thyroid disorders (2009). Treatment Guidelines From The Medical Letter, 7(84): 57–64.
Jameson JL, Weetman AP (2012). Disorders of the thyroid gland. In DL Longo et al., eds., Harrison's Principles of Internal Medicine, 18th ed., vol. 2, pp. 2911–2939. New York: McGraw–Hill.
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Villar HCCE, et al. (2007). Thyroid hormone
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August 7, 2012
Kathleen Romito, MD - Family Medicine & Matthew I. Kim, MD - Endocrinology
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