Understanding the difference between Hypothyroidism and Hyperthyroidism

Both hypothyroidism and hyperthyroidism occur as a result of a thyroid hormone imbalance. Simply put, hypothyroidism means that your thyroid gland isn't producing enough hormone, while hyperthyroidism means your thyroid is producing too much of the hormone. Either way, the condition affects the metabolism of the body.

According to the U.S. Department of Health and Human Services, approximately five percent and one percent of the U.S. population has hypothyroidism and hyperthyroidism, respectively. Women are more likely than men to develop either one of the conditions. The risk of developing either hypothyroidism or hyperthyroidism increases with age and family history.

The Thyroid Gland. The thyroid gland is a small butterfly-shaped organ, which lies near the front of the neck below the voice box. Because the thyroid is one of the glands of the endocrine system, it releases hormones into the bloodstream. Thyroid hormones help regulate your metabolism, and affect practically every organ in the body.


When you have an underactive thyroid, the condition is called hypothyroidism. With this condition, you'll have a marked decrease in circulating thyroid hormones, and your metabolism will slow.

Although symptoms vary from person-to-person, common hypothyroidism symptoms include weight gain, cold intolerance, fatigue, puffy face, dry hair, thinning hair, constipation, slowed heart rate, decreased sweating, irregular or heavy menstrual periods, impaired fertility, or depression.


When you have an overactive thyroid, the condition is called hyperthyroidism. Instead of having a deficiency of thyroid hormones as is the case with hypothyroidism, with hyperthyroidism, you'll have excess thyroid hormones circulating through your body. Your metabolism will be revved up.

Common hyperthyroidism symptoms include heat intolerance, weight loss, trouble sleeping, fatigue, muscle weakness, nervousness, irritability, hand tremors, rapid or irregular heartbeat, mood swings, or frequent diarrhea and bowel movements. In addition, you may have an enlarged thyroid, called a goiter, which may make your neck look swollen. Some symptoms, like fatigue, overlap between hypothyroidism and hyperthyroidism.


Your doctor will perform blood work to diagnose thyroid disease. The TSH test is typically the first test performed by your doctor due to its accuracy and sensitivity. A TSH test reading below normal indicates that a person has hyperthyroidism, while a TSH reading above normal is an indication of hypothyroidism.

To determine the cause or confirm a hypothyroidism diagnosis, your doctor may conduct additional tests, such as the T4 test. The T4 test is used to measure the actual level of thyroid hormone circulating in the blood stream. A T4 level of lower than normal may be an additional indication of hypothyroidism.


Hypothyroidism can usually be easily treated with thyroid hormone replacement therapy. Most patients notice improvement within a week, with all symptoms disappearing within a few months. Treatment may consist of visiting your doctor frequently initially to adjust the dosage.

Depending on your age, the cause of your condition, other health conditions, and the level of thyroid hormone your body is producing, your doctor will choose one of three main treatment methods when treating hyperthyroidism. Radioactive iodine and antithyroid medicine are the two most commonly used treatment methods. Less common, surgery may need to be done to correct the hyperthyroidism symptoms.

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