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Quick Facts



The Manual's Editorial Staff

Last full review/revision Jul 2020| Content last modified Jul 2020
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Your thyroid is a gland below the Adam’s apple in your neck.

Your thyroid releases thyroid hormones. The hormones control how fast your body’s chemical functions work (metabolic rate). Almost every cell in your body needs thyroid hormones. Among many other things, thyroid hormones help control:

  • How fast you burn calories

  • How fast your heart beats

  • Your body temperature

Iodine is needed by your thyroid gland in order to make thyroid hormones. You need only a tiny amount of iodine. But if your thyroid gland doesn't get iodine, it won't make enough thyroid hormones.

Locating the Thyroid Gland

Locating the Thyroid Gland

What is hypothyroidism?

Hypothyroidism is when your thyroid doesn't make enough thyroid hormones.

  • Hypothyroidism is common, especially among older women

  • A disease called Hashimoto thyroiditis is the most common cause

  • You may feel tired, sluggish, and cold

  • Hypothyroidism usually develops slowly

  • Blood tests can confirm you have hypothyroidism

  • You may need to take thyroid hormone pills for the rest of your life

What causes hypothyroidism?

Causes of hypothyroidism include:

  • Surgery or radiation therapy to remove or stop the thyroid

  • Lack of iodine

  • Pituitary gland problems

In Hashimoto thyroiditis, your body's immune system mistakenly attacks your thyroid. This type of disease is called an autoimmune disease.

Lack of iodine is rare in modern countries. Most countries put a little iodine in salt so everybody gets enough. There's also iodine in seafood. People in some poor countries far from the sea are at risk of not getting enough iodine.

The pituitary gland in your brain makes a hormone called TSH that tells your thyroid to make thyroid hormones. If you have a problem with your pituitary gland, it might not make TSH and you'll get hypothyroidism.

Who can get hypothyroidism?

Almost anyone can get hypothyroidism, but it's more common in older people. Sometimes, hypothyroidism can happen in:

  • Newborn babies

  • Women during or just after pregnancy

  • People with other autoimmune diseases such as rheumatoid arthritis

What are the symptoms of hypothyroidism?

Not enough thyroid hormones cause your body functions to slow down, which can affect how you look, sound, or feel.

Symptoms that affect the way you look or sound may include:

  • Puffy eyes and face and droopy eyelids

  • Thin, rough, dry hair

  • Rough, dry, scaly, thick skin

  • Hoarse voice and slow speech

Symptoms that affect the way you feel may include:

  • Constipation

  • Getting cold easily

  • Tingling or hurting hands

  • Slow heart beat

  • Confusion, forgetfulness, and depression

If not treated, hypothyroidism can eventually cause:

In older people, confusion and forgetfulness may be mistaken for Alzheimer disease or some other kind of dementia.

How can doctors tell if I have hypothyroidism?

Doctors will do:

How do doctors treat hypothyroidism?

Doctors treat hypothyroidism with:

  • Thyroid hormone pills

After you start the pills, your doctor will gradually adjust the dose based on your TSH level. It's important to talk to your doctor about medicines that interfere with absorbing thyroid hormone. Such medicines include iron, calcium, and some antacids.

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