What Is Thyrotoxicosis?

Medically Reviewed by Michael Dansinger, MD on December 12, 2022
3 min read

Your thyroid gland (a small butterfly-shaped organ in the lower front of your neck) makes hormones that help your body use energy, stay warm, and keep your organs working the way they should. Thyrotoxicosis is when you have way too much of those hormones in your blood.

This happens most often because your thyroid gland makes too much. That’s a condition called hyperthyroidism.

Graves’ disease: This condition is the most common cause of hyperthyroidism -- and thyrotoxicosis. It leads your immune system to mistake the cells of your thyroid gland for invaders and attack them with antibodies (a type of protein). It’s not clear why this happens, but it makes the gland grow and make too much thyroid hormone. The condition tends to run in families, so your genes may play a part in whether you get it.

Nodules: Growths called nodules can develop on your thyroid and affect how much hormone the gland makes. A single hyperfunctioning nodule is called toxic nodular adenoma., while multinodular goiter or Plummer’s disease means you have a number of them.

Struma ovarii: This is a rare type of ovarian tumor that’s made mostly of thyroid tissue. In some cases, it can cause hyperthyroidism.

Thyroiditis: A virus or bacteria, certain medications (like lithium), or even your own immune system can inflame your thyroid gland and make it release too much hormone into your bloodstream.

Thyroid supplement: Some people take thyroid hormone in pill form to treat a medical condition, like hypothyroidism (when your thyroid doesn’t make enough hormone). You can have too much in your blood if your prescription is off or you don’t take the medication as directed.

Normally, thyroid hormones help you burn energy at the right speed. High levels can affect your body in lots of different ways.

In general, they speed things up -- like your heart, which often beats faster. You might poop and sweat more, feel irritable and nervous, and have shaky hands and weaker muscles. You may lose weight because you don’t eat enough calories to match your faster metabolism.

Graves’ disease can also trigger thyroid eye disease with red, watery eyes that bulge out with swollen lids.

Your doctor will ask about your symptoms and medications you take, and check to see if your pulse is too fast or your thyroid is too big. After that, a simple blood test that measures the amount of thyroid stimulating hormone, or TSH, in your blood can help your doctor know for sure if you have thyrotoxicosis.

You might need more blood tests to find the exact cause. In some cases, your doctor also may want to get a better look at your thyroid gland with an ultrasound. That’s a machine that uses sound waves to make images of the inside of your body.

For Graves’ disease and other types of hyperthyroidism, drugs called antithyroid agents can help keep the gland from making too much hormone.

Radioactive iodine that’s usually swallowed in a capsule can destroy thyroid cells. This treatment may sound scary, but it has a long history and is generally safe and works well. Beta-blockers help ease certain symptoms, like a faster pulse and shaky hands, but don’t do anything to lower your hormone levels.

In serious cases, you and your doctor may decide to remove part or all of your thyroid gland with surgery to ease your symptoms.

Symptoms of low blood sugar -- tremors and sweating -- can be easily confused with symptoms of high thyroid hormone levels. You may mistakenly think you have low blood sugar and eat extra food that makes your blood sugar spike. That can be bad for your health and mask your thyroid problems.

The faster metabolism caused by thyrotoxicosis can affect your diabetes medicines and make them move more quickly through your system. That could mean your normal dosage of insulin or other medicine won’t be enough to control your blood sugar. Your doctor can help you manage this.