What Are the Causes of Hyperthyroidism?

Medically Reviewed by Carol DerSarkissian, MD on May 10, 2021

Hyperthyroidism is another name for an overactive thyroid. It’s when the butterfly-shaped gland in your neck produces too much thyroid hormone.

This can happen for many different reasons. You’re more likely to develop it if you’re a woman, if you’ve had other thyroid problems, or if you’re over the age of 60.

It’s important to work with your doctor to find the cause because it can affect your treatment.

What Your Thyroid Does

Two major hormones that affect how your body works are produced in your thyroid. These are called thyroxine (T-4) and triiodothyronine (T-3). Their job is to help keep your heart rate, body temperature, and other body functions working right. They do this by helping your body use carbohydrates and fats the way it’s supposed to.

Another important hormone your thyroid produces is called calcitonin, and this helps keep a healthy amount of calcium in your blood.

Why Your Body Might Make Too Much Thyroid Hormone

Most people with hyperthyroidism have a condition called Graves’ disease. This accounts for 70% of the cases.

Normally, the antibodies in your blood go after bacteria, but if you have Graves’ disease, the antibodies turn on your thyroid instead. This causes the gland to produce too much T-4 thyroid hormone.

Doctors aren’t sure why some people get Graves’ disease, but it tends to run in families. It’s also more common in young women.

Other conditions linked to hyperthyroidism include:

Plummer’s disease. This happens when one or more sections on your thyroid develop lumps that aren’t cancer. These lumps can make your thyroid grow bigger and produce too much T-4 hormone.

Plummer’s disease is more common in older people.

Thyroiditis. This can push your thyroid into overdrive for a short period of time. With this condition, your thyroid is swollen for unknown reasons. This swelling can force hormones out of your thyroid and into your bloodstream.

Thyroiditis can happen:

WebMD Medical Reference



Mayo Clinic: “Hyperthyroidism (overactive thyroid).”

Cambridge Dictionary: “Antibody.”

American Thyroid Association: “Hyperthyroidism (Overactive).”

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