Thyroid appearing in a woman's neck

Hypothyroidism

Also known as an underactive thyroid gland

Hypothyroidism occurs when your thyroid gland does not produce enough thyroid hormone. Since thyroid hormones regulate your body's metabolism and temperature, when a deficiency occurs, your body has trouble using energy and staying warm. Common symptoms include fatigue, feeling cold, constipation, and slight weight gain. 

The main blood test used to diagnose hypothyroidism is the thyroid-stimulating hormone (TSH) test. TSH, which is produced and released by the pituitary gland, rises when it detects low levels of thyroid hormone.

The treatment of hypothyroidism involves taking a daily medication that replaces the missing thyroid hormone in the body. Levothyroxine is the most commonly prescribed thyroid hormone replacement drug.

Frequently Asked Questions

  • What causes hypothyroidism?

    While there are many causes of hypothyroidism, the main cause in the U.S. is an autoimmune disease called Hashimoto's thyroiditis. With this disease, a person’s own immune system misguidedly attacks their thyroid gland. Other causes of hypothyroidism include the use of certain medications, surgical removal of the thyroid gland, and radiation therapy, to name a few.

  • Is hypothyroidism an autoimmune disease?

    Not necessarily. Hypothyroidism describes a thyroid gland that produces too little or no thyroid hormone. While the primary cause of hypothyroidism in the United States is an autoimmune disease called Hashimoto's thyroiditis, there are other causes of hypothyroidism that are not autoimmune related.

  • How do I lose weight with hypothyroidism?

    Losing weight with hypothyroidism can be tricky. Research suggests that even if your TSH level is within the "normal" range, slight variations may contribute to weight gain. After partnering with a doctor who understands your situation, some key approaches to bolstering your metabolism include adjusting your eating and sleeping patterns and improving your digestion with high-fiber foods.

  • How is hypothyroidism treated?

    The treatment of hypothyroidism involves taking a drug to bring your thyroid-stimulating hormone (TSH) level back to normal. Doctors usually prescribe levothyroxine, which is the synthetic form of the thyroid hormone T4 (thyroxine). Levothyroxine is an oral drug taken once daily that is available in both generic and brand-name formulations.

  • Is hypothyroidism a genetic disease?

    Hypothyroidism has many causes and is not by itself a genetic disease. That said, mutations in genes involved in the immune system likely play a role in the development of Hashimoto’s thyroiditis. This autoimmune disease is the leading cause of hypothyroidism in the United States.

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Page Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Thyroid Association. Hypothyroidism (underactive).

  2. Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement. Thyroid. 2014;24(12):1670–1751. doi:10.1089/thy.2014.0028

  3. Sanyal D, Raychaudhuri M. Hypothyroidism and obesity: An intriguing link. Indian J Endocrinol Metab. 2016;20(4):554–557. doi:10.4103/2230-8210.183454

Additional Reading