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Hypothyroidism vs. hyperthyroidism

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Hypothyroidism overviewHyperthyroidismKey differencesTreatmentsSummary
Hypothyroidism, or underactive thyroid, is when the thyroid gland produces too few thyroid hormones. This can slow some bodily functions. Hyperthyroidism, or overactive thyroid, is when it produces too many thyroid hormones and speeds up certain functions.
Medically reviewed by Alana Biggers, M.D., MPH
Updated on April 12, 2023

The thyroid is a small organ at the front of your neck. It produces hormones that affect every part of your body. Thyroid hormones help regulate your energy levels, control your temperature, and keep your organs and muscles working as they should.

In this article, learn about hypothyroidism and hyperthyroidism, their differences, and available treatment options.

Hypothyroidism overview

Doctor examining thyroid or lymph glands in patient's neck
mixetto/Getty Images

Hypothyroidism occurs when your thyroid doesn’t make enough thyroid hormones for your body to function optimally, and many body functions slow down.

Nearly 5 out of 100 people in the United States ages 12 years and older have hypothyroidism.

Signs and symptoms

Hypothyroid symptoms vary from person to person and are often mild, especially at the beginning. You may not even notice them for several months or even years. Many of these symptoms are very common and may not indicate hypothyroidism. 

  • fatigue
  • depression
  • weight gain
  • thinning hair
  • dry skin or lips
  • fertility concerns
  • slowed heart rate
  • muscle and joint pain
  • difficulty tolerating cold
  • heavy or irregular menstrual periods

Causes and risk factors

Several things can cause your thyroid to produce less thyroid hormone than it should, including

  • thyroid radiation treatments
  • thyroiditis, an inflamed thyroid
  • too little or too much iodine in your diet
  • hypothalamus or pituitary gland disorders
  • surgical removal of part or all of your thyroid
  • Hashimoto’s disease, an autoimmune condition
  • conditions affecting a baby before birth, known as a congenital condition

Certain drugs can also decrease thyroid production, such as some heart medications, bipolar disorder medications, and chemotherapy treatments.

Certain things make it more likely for you to develop hypothyroidism:

  • age over 60
  • history of thyroid issues
  • being assigned female at birth
  • family history of thyroid disease
  • pregnancy within the last 6 months
  • certain health conditions, such as 
    • type 1 or type 2 diabetes
    • rheumatoid arthritis
    • Sjögren’s disease
    • Turner’s syndrome
    • pernicious anemia
    • celiac disease
    • lupus

Hyperthyroidism overview

Hyperthyroidism occurs when the thyroid makes too much thyroid hormone, and many of your body’s functions speed up.

Hyperthyroidism is not as common as hypothyroidism — 1 out of 100 people in the United States ages 12 years and older has hyperthyroidism.

Signs and symptoms

Symptoms of hyperthyroidism vary from person to person and may include:

  • weight loss, even with an increased appetite
  • goiters (enlargements in the neck)
  • frequent bowel movements 
  • irregular or fast heartbeat
  • irritability or nervousness
  • difficulty tolerating heat
  • excessive sweating
  • muscle weakness
  • difficulty sleeping
  • shaky hands
  • fatigue

Older adults may have different symptoms than younger people. For example, older adults may have a decreased appetite, or their symptoms may look like depression.

Causes and risk factors

Hyperthyroidism can be due to:

  • Graves’ disease
  • excess iodine intake
  • overactive thyroid nodules
  • too much thyroid hormone medication
  • thyroiditis (an inflamed thyroid gland)
  • a noncancerous pituitary gland tumor

Hyperthyroidism is more common under certain conditions, such as:

  • being over 60 years old
  • nicotine use
  • pernicious anemia
  • being assigned female at birth
  • family history of thyroid disease
  • pregnancy within the past 6 months
  • certain medical conditions, such as: 
    • type 1 or type 2 diabetes
    • primary adrenal insufficiency

Key differences 

In hyperthyroidism, your thyroid becomes hyperactive, and some of your body’s functions speed up.

In hypothyroidism, your thyroid hormone production slows down, along with some of your body’s functions.

If your doctor suspects your thyroid is not functioning correctly, they will order a blood test to check your thyroid stimulating hormone (TSH) level. Changes in your TSH level are some of the first signs of thyroid issues — they often occur before other levels get too low or too high and symptoms appear: 

  • A high TSH level indicates hypothyroidism.  
  • A low TSH level usually indicates hyperthyroidism. Sometimes, a low TSH level can occur due to a pituitary gland abnormality. In that case, the pituitary gland prevents the thyroid from producing TSH, causing a condition known as pituitary hypothyroidism.

A 2023 review suggests a considerable variation in the “normal range” for TSH over a lifetime. Decreasing levels of TSH in younger people can lead to heart disease and other heart-related conditions, while decreasing levels in older adults may be beneficial. Further studies to confirm where these “normal” ranges should be is necessary.

Treatments

If you have hypothyroidism, your doctor may recommend replacing the hormones your body can no longer produce with levothyroxine. Levothyroxine is available as a pill, capsule, or liquid. Doctors recommend you take this first thing in the morning before eating anything.

You will need occasional blood tests to determine whether the levothyroxine dose is working. Your doctor may want to increase or decrease your dosage based on these blood tests. 

If you take the recommended dose, levothyroxine can usually completely manage your hypothyroidism. 

Always talk with your doctor before stopping your levothyroxine dose. It’s also important not to take more than the recommended dose as it can lead to serious problems, such as osteoporosis or abnormal heart rhythms.

Need a refill for levothyroxine (Synthroid)? You may be able to get an online prescription through Optum Perks in as little as 15 minutes with no video or appointment needed. Learn more here.

If you have hyperthyroidism, your doctor may recommend different treatments, depending on what is causing the hyperthyroidism, other health conditions present, and your preferences. These may include:

  • Radioactive iodine therapy (RAI). 
  • Surgery to remove part or all of your thyroid (a thyroidectomy).
  • Antithyroid drugs, which are becoming more popular as treatment options. These include:
  • Radiofrequency ablation is a new way to treat hyperthyroidism caused by thyroid nodules. Doctors mainly use this when medication and surgery do not work, but it is not currently widely available.

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Summary

Hyperthyroidism and hypothyroidism occur when your thyroid does not produce thyroid hormones as it should. Hyperthyroidism happens when your thyroid makes too much, and hypothyroidism occurs when your thyroid makes too little. 

Symptoms and treatments depend on which type of thyroid disease you have. Talk with your doctor about what treatments are right for you.

Download the free Optum Perks Discount Card to save up to 80% on some prescription medications.

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