If your thyroid–a butterfly-shaped gland in the neck that helps control metabolism–is underactive, you may experience weight gain, constipation, cold sensitivity, or fatigue (hypothyroidism). If it's overactive, you may lose weight quickly, sweat a lot, have a fast heartbeat, or feel nervous or moody (hyperthyroidism). Luckily, thyroid treatments are often effective.

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19 Signs Your Thyroid Isn’t Working Right

Crabby, gaining weight, and unable to concentrate? It could be a problem with that little gland in your neck.

11 Celebs With Thyroid Disease–and How They Knew Something Was Wrong

Don’t ignore extreme exhaustion and unexplained fluctuations in weight. They could signal trouble with a tiny organ in your neck that keeps your metabolism humming along.

9 Things You Need to Know About Your Thyroid

Got weight gain or unexplained fatigue? That butterfly-shaped gland in your neck may be to blame. Here's what it controls, how to tell if it's healthy—and how to keep it that way.

15 Thyroid Cancer Facts Everyone Should Know

Thyroid cancer diagnoses are on the rise, and most cases are in younger adults. Here's what you should know about detection, treatment, and recovery.

If You Get Frequent Headaches, You May Want to Have Your Thyroid Tested

New research has found that people with headache disorders (especially migraines) are more likely to be diagnosed with hypothyroidism.

More on Thyroid

10 Common Myths About Thyroid Disease You Probably Believe

From worrisome neck lumps to the best treatment method, endocrinologists uncover the truth about the most common—and the strangest—thyroid myths.