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Hyperthyroidism (overactive thyroid)

What is Hyperthyroidism?

Hyperthyroidism is a condition describing the overproduction of thyroid hormone from the thyroid gland.

What Are Signs and Symptoms Hyperthyroidism?

Symptoms are different for each person. Here are the most common ones:

  • Nervousness
  • Irritability
  • Sweating more than normal
  • Thinning of the skin
  • Fine, brittle hair
  • Weak muscles, especially in the upper arms and thighs
  • Shaky hands
  • Fast heartbeat (palpitations)
  • High blood pressure
  • More bowel movements than normal, diarrhea
  • Weight loss
  • Trouble dealing with the heat
  • Problems sleeping
  • Prominent eyes
  • Sensitivity to bright light
  • Confusion
  • Irregular menstrual cycle in women
  • Tiredness and lack of energy (fatigue)
  • Larger than normal thyroid gland (goiter)

How is Hyperthyroidism Diagnosed?

At the UCLA Endocrine Center, you will meet with an endocrinologist who will ask about your past health, including your medications and diet, and perform a comprehensive physical exam.

Blood tests can help diagnose hyperthyroidism. Laboratory tests to determine thyroid function include:

  • Thyroid Stimulating Hormone (aka TSH) helps indicate whether the thyroid is working correctly
  • Measurements of the two forms of thyroid hormone, T4 and T3
  • If indicated, measurements of specific antibodies targeted to the thyroid and its receptors

The workup may also include neck ultrasound to assess for thyroid nodules that could be overproducing thyroid hormone.

What Causes Hyperthyroidism?

Hyperthyroidism has several causes. These may include:

Graves' Disease

This is an autoimmune disorder. It is the most common cause of hyperthyroidism. It happens when an antibody overstimulates the thyroid. This condition is most often found in young to middle-aged women. It also tends to run in families.

Toxic nodular goiter

This condition happens when one or more lumps (nodules) of the thyroid gland become too active. Health experts don't know what causes this to happen. In most cases, the nodules are not cancer (benign). But in rare cases the overactive thyroid tissue is cancer.


This is a general term that refers to inflammation of the thyroid. Depending on the severity, thyroiditis may or may not produce any symptoms or need to be treated. The inflammation releases an excessive amount of thyroid hormone, leading to temporary hyperthyroidism. As the thyroid “burns out,” the thyroid then often becomes underactive.

Less common causes of hyperthyroidism include:

  • Taking too much thyroid hormone medicine to treat an underactive thyroid
  • Having too much iodine in your diet or in medicines, such as amiodarone
  • Having a noncancer tumor in the pituitary gland that makes your thyroid overactive

What are Causes of Thyroiditis?

Hashimoto's thyroiditis (chronic lymphocytic thyroiditis)

Hashimoto’s thyroiditis is a type of inflammation of the thyroid gland that results from an autoimmune process.  It is the most common cause of Hashimoto’s hypothyroidism (in which the inflammation results in an underactive thyroid gland) in the U.S.  However, some individuals with Hashimoto's thyroiditis may never develop hypothyroidism and thus never have any symptoms.

Infectious thyroiditis

Infectious thyroiditis is inflammation of the thyroid gland resulting from an infection in the thyroid.  Patients with this will usually have neck pain, enlargement of the thyroid gland, and symptoms of an infection, such as fever and generalized body aches.

Painless thyroiditis

Painless thyroiditis is an inflammation of the thyroid gland in which there is a short period of both hyperthyroidism and hypothyroidism.  The thyroid gland is not painful.  Both usually resolve without treatment.  Painess postpartum thyroiditis refers to this disorder when it occurs in women who were recently pregnant.

Drug-induced or radiation thyroiditis

Inflammation of the thyroid gland may also occur in individuals who are taking certain medications, including amiodarone, lithium, and interferon.  Radiation of the neck can also result in thyroiditis.  The hyperthyroid and hypothyroid phases of thyroid inflammation can be managed usually with medications alone.

Fibrous thyroiditis (Riedel's thyroiditis)

Fibrous thyroiditis is an extremely rare condition in which the thyroid becomes hardened from a significant inflammatory process in the thyroid that extends locally in the neck.  Surgery may be required to treat this condition.

How is Hyperthyroidism Treated?

Treatment will depend on your symptoms, age, and general health. It will also depend on how severe the condition is.

Treatment may include:

  • Medicine. It can help lower the level of thyroid hormones in the blood.
  • Radioactive iodine. It comes in the form of a pill or liquid. It slowly destroys the cells of the thyroid gland so that less thyroid hormone is made.
  • Surgery. You may need to have all or part of your thyroid removed.
  • Beta blockers. These medicines block the action of the thyroid hormone on the body. That helps with rapid heart rate and palpitations.

Frequently Asked Questions

What are possible complications of hyperthyroidism?

If your hyperthyroidism is not treated, these complications may happen:

  • Thyroid crisis, when symptoms get worse because of stress or illness
  • Heart problems, such as an abnormal rhythm or heart failure
  • Weak, brittle bones (osteoporosis)
  • Pregnancy problems, such as miscarriage, early delivery, and preeclampsia or high blood pressure

Contact us for more information or to request an appointment.

Tips to help you prepare for your visit:

  • Know the reason for your visit and what you want to happen.
  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.
  • Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
  • Ask if your condition can be treated in other ways.
  • Know why a test or procedure is recommended and what the results could mean.
  • Know what to expect if you do not take the medicine or have the test or procedure.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.

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Learn more about the UCLA Division of Endocrinology, Diabetes & Metabolism.


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Pouyan Famini, MD 

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Torrance (South Bay Endocrinology)


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Westlake Village


Yaroslav Gofnung, MD 

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Amy Y. Chow, MD 

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