Hyperthyroidism vs. Hypothyroidism: Here’s How to Tell The Difference | Hartford HealthCare

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April 29, 2021

By Dr. H. Nail Aydin
Surgical Oncology
Hartford HealthCare Medical Group
Windham Hospital

Thyroid disease affects approximately 20 million people in the United States, but many who have thyroid disease don’t know it. A diagnosis is important because the thyroid can affect every system in your body.

The two most common types of thyroid disorders are hyperthyroidism and hypothyroidism. And while they sound the same, they are very different.

First, what is the thyroid and why is it important?

It is a gland in the front of your neck that is part of the endocrine system, which controls the hormones in your body. Thyroid hormones help you metabolize fats, proteins, and carbohydrates and help maintain your blood pressure, body temperature, and heart rate. Your thyroid does a lot of work.

What’s the difference between hyperthyroidism and hypothyroidism?

Hyperthyroidism is an overactive thyroid (when it produces too much thyroid hormone). Hypothyroidism is an underactive thyroid (when it does not produce enough). Hypothyroidism is more common than hyperthyroidism.

Although the two conditions have different signs and symptoms, sometimes they overlap. For example, enlargement of the thyroid, called a goiter, can happen in both types of thyroid disease.

Let’s take a look at symptoms.


  • Hand tremor.
  • Weight loss.
  • Nervousness.
  • Fast heart rate.
  • Trouble sleeping.
  • Brittle skin.
  • Muscle weakness.
  • Irritability.
  • Weaker or less frequent menstrual periods.


  • Constipation.
  • Fatigue.
  • Cold sensitivity.
  • Weight gain.
  • Dry skin.
  • Forgetfulness.

What Causes Hyperthyroidism and Hwindypothyroidism?

The causes and treatments of hyperthyroidism and hypothyroidism are very different.

Graves’ disease is the most common cause of hyperthyroidism. It is an autoimmune disease in which your immune system attacks the thyroid, causing it to grow and release too much hormone.

Other causes of hyperthyroidism include:

  • Small masses within the thyroid (called a toxic nodular goiter).
  • Thyroiditis, an inflammation of the thyroid due to a virus.
  • Postpartum thyroiditis (after giving birth).
  • Taking too much thyroid hormone.

Hypothyroidism occurs when your thyroid is either no longer working properly or has been removed or destroyed for medical reasons (such as cancer). It is more common in women and with age. Hashimoto’s thyroiditis, another autoimmune disease, is the most common cause of hypothyroidism in the U.S.

Other causes of hypothyroidism:

  • Previous radioiodine or surgical treatment for hyperthyroidism, thyroid cancer or other thyroid disease.
  • Previous radiation for other head and neck cancer.
  • Conditions that affect the pituitary gland in the brain (such as Sheehan’s syndrome).
  • Hypothyroidism present at birth, or congenital hypothyroidism.
  • Medications, including amiodarone (Pacerone), lithium, and anti-epilepsy drugs.

How Are Hyperthyroidism and Hypothyroidism Diagnosed and Treated?

A blood test for thyroid stimulating hormone (TSH, also called serum thyrotropin) is used to screen for thyroid problems. Because TSH stimulates production of your thyroid hormones, TSH is high when your body is not making enough thyroid hormone (hypothyroidism) and low when it makes too much (hyperthyroidism).

The treatment of hyperthyroidism starts with treating the symptoms. Beta blockers are commonly prescribed to start. These drugs can slow heart rate, decrease tremors and improve irritability.

Other treatments depend on the cause of the hyperthyroidism. Options include methimazole (Tapazole) if you have Graves’ disease.

If medication doesn’t work or if hyperthyroidism is due to other causes, other options include destroying the thyroid cells with radioactive iodine or removing the gland with surgery.

Hypothyroidism is commonly treated with supplemental thyroid hormone. The synthetic (man-made) version is called L-thyroxine or levothyroxine. Your doctor will select a dose based on your age and weight, then monitor your TSH periodically to see if it needs to be adjusted. The goal is to get your TSH back in the normal range and improve your symptoms.

Surgery is a treatment option for hyperthyroidism. For some types of hyperthyroidism, surgery entails partial removal of the half of your thyroid gland (known as a lobectomy) with the adenoma. For nearly all other types of hyperthyroidism, including Graves’ disease, the surgery is a nearly total thyroidectomy.

A total thyroidectomy is the only option that gives an immediate cure of hyperthyroidism.

Though surgery is not the most common method for treating hyperthyroidism, you may be a good candidate based on the specific cause of your condition and your preferences. It’s important to talk to your doctor about the benefits and risks of medications vs. a thyroidectomy.


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