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What's the Difference Between Overactive and Underactive Thyroid?

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Overactive and Underactive Thyroid: What's the Difference? Adiano/Fotolia

The thyroid is a butterfly-shaped gland located in the front of the neck. It produces and distributes hormones that play a large role in many important functions. It helps with blood circulation, body temperature, bowel movements, brain activity, breathing, digestion and muscle control. So it’s no surprise that a thyroid disorder can cause problems all over the body.

The most common thyroid disorders are hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid).

What is hypothyroidism or underactive thyroid?

In medical terms, hypo means deficient. Hypothyroidism is caused by an underproduction of thyroid hormones. This is problematic as your body's energy production requires a certain amount of thyroid hormones.

With hypothyroidism, people can experience brittle nails, constipation, decreased menstrual flow, dry hair and skin, fatigue, goiter (swelling in the front of the neck), muscle cramps and weight gain, according to EverydayHealth.com. An underactive thyroid can also affect one’s mood, resulting in depression or memory problems.

The most common source of hypothyroidism is Hashimoto’s disease, also called Hashimoto's thyroiditis. Here, the immune system creates antibodies designed to destroy thyroid cells and prevent them from producing thyroid hormones.

Left untreated, hypothyroidism can raise cholesterol levels and make having a heart attack or stroke more likely. During pregnancy, untreated hypothyroidism can harm the baby, according to the University of Maryland Baltimore Washington Medical Center on its website MYBWMC.org.

Treatment for hypothyroidism is typically thyroid replacement therapy. Medications emulate and replace the thyroid hormone’s many jobs, making up for the deficiency, wrote FoxNews.com. Hypothyroidism treatment usually lasts a lifetime.

What is hyperthyroidism or overactive thyroid?

Hyper, in medical terms, means too much. Hyperthyroidism happens when the thyroid becomes overactive and produces too many hormones.

EverydayHealth.com wrote “think of hyperthyroidism as a racing car engine. With an overactive thyroid, all body functions generally speed up.”

MYBWMC.org stated that women are affected by hyperthyroidism 10 times more than men.

Given the thyroid’s job in our bodies, this hormone overload can be responsible for any number of physical changes. Overactive thyroid symptoms include dry skin, high blood pressure, irregular menstrual periods, nausea and vomiting. They can also include nervousness, temperature sensitivity, thinning or loss of hair, and weight loss.

With your metabolism racing like a car engine, you stay excited and restless. However, the longer the body is revved up, the longer it will remain too stimulated, and eventually fatigue takes over.

The most common form of hyperthyroidism is Graves’ disease, which is an autoimmune condition. Some people with Graves’ disease have a goiter, and their eyes may appear bulged out due to inflammation, wrote EverydayHealth.com.

Hyperthyroidism is generally treated with anti-thyroid medication. These medications prevent the thyroid from making an overabundance of hormones. Thyroid removal surgery may be dictated in some cases.

Without treatment, hyperthyroidism can result in serious bone and heart problems and a life-threatening condition called thyroid storm.

Fortunately both hypothyroidism and hyperthyroidism are manageable if properly treated.


"Hypothyroidism Versus Hyperthyroidism | Fox News." Fox News. FOX News Network, 2012. Web. 18 Jan. 2016.

Provost, Dr. Bridgette C. "Health Talk: Understanding Over Active and Under Active Thyroid." Health Talk: Understanding Over Active and Under Active Thyroid. Web. 18 Jan. 2016.

Shimer Bowers, Elizabeth. "Hypothyroidism vs. Hyperthyroidism: What's the Difference?" EverydayHealth.com. Web. 18 Jan. 2016.

"Fatigued or Full Throttle: Is Your Thyroid to Blame?" WebMD Boots. Web. 18 Jan. 2016.

Reviewed January 25, 2016
by Michele Blacksberg RN
Edited by Jody Smith

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We value and respect our HERWriters' experiences, but everyone is different. Many of our writers are speaking from personal experience, and what's worked for them may not work for you. Their articles are not a substitute for medical advice, although we hope you can gain knowledge from their insight.

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