How Thyroid Disease Causes Dry Mouth

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If you have thyroid disease, then chances are good that you also have persistent xerostomia (dry mouth).

In fact, while there are many causes of dry mouth, one study found that about half of people who are diagnosed with xerostomia have thyroid disease.

To compound matters, treatment for thyroid disease can also trigger xerostomia. Dry mouth is not life-threatening, but it can make swallowing difficult, cause bad breath, and even lead to complications like cavities and oral infections.

This article explains the link between thyroid disease and dry mouth. It also points out the specific thyroid conditions that most often lead to dry mouth and how you can ease the discomfort.

thyroid and dry mouth
Verywell / Gary Ferster

The Link To Saliva

Among the many effects of thyroid disease is a diminished production and release of saliva from the salivary glands. And this results in a dry mouth. Thyroid patients who spit, for example, may not experience full replenishment of their saliva until hours later.

This is believed to be related to slowed metabolism associated with a hypothyroid disease, or the state of have an underactive thyroid. Untreated or partially treated hyperthyroidism can cause dry mouth as well, though the reason is unclear. Hyperthyroidism is the state of having an overactive thyroid.

Thyroid Conditions

While dry mouth is most often associated with hypothyroidism, research studies show that it can also occur with a variety of thyroid conditions, including those that cause hyperthyroidism. Some types of thyroid disease that are associated with dry mouth include:

  • Hashimoto's thyroiditis (HF): HF is an autoimmune condition that causes hypothyroidism due to decreased function of the thyroid gland.
  • Subacute thyroiditis: Inflammation of the thyroid gland, caused by granulomatous thyroiditis, HF, inflammation, medications, or an infection, can cause hypothyroidism or hyperthyroidism.
  • Subclinical hypothyroidism: People with early-stage hypothyroidism or hyperthyroidism may have mild or unnoticeable effects, including dry mouth.
  • Grave's disease: As a common type of overactive thyroid, Grave's disease causes weight loss, hyperactivity, and insomnia as well as dry mouth.


Dry mouth can also occur as a result of some thyroid disease treatments:

  • Radiation therapy: Radiation, which is often used for the treatment of thyroid cancer, can affect the thyroid glands and may damage the salivary glands, reducing the amount of saliva.
  • Radioiodine therapy: Radioiodine is used to treat thyroid cancer and some types of hyperthyroidism, often resulting in hypothyroidism and decreased salivary gland function.
  • Thyroid hormone replacement therapy: Usually, dry mouth can improve with treatment of hypothyroidism. But in some cases, excessive thyroid hormone replacement can also cause dry mouth.


Aside from the obvious, effects of dry mouth can include:

  • Bad breath
  • Cavities, gum disease*
  • Chapped, split, or cracked lips*
  • Decreased ability to speak fluently and comfortably
  • Diminished enjoyment of food
  • Impaired ability to chew and swallow food
  • Oral infections, mouth sores*

*With severe cases of dry mouth

While everyone gets a dry mouth now and then, it could be a symptom of thyroid disease or another underlying health problem if it lasts for weeks at a time. If you notice that you've had a persistent sensation of dry mouth, talk to your healthcare provider.


Besides getting the right treatment for your thyroid disease (one that controls your condition, as well as its side effects), there are other ways to ease dry mouth. Try some of these simple tactics:

  • Abstain from foods that can make dry mouth worse, such as salty foods and dry meats.
  • Avoid tobacco, alcohol, carbonated beverages, juices, and caffeine, all of which may dry out the mouth. 
  • Drink lots of fluids to keep your mouth moist.
  • Eat sugar-free saliva stimulants, such as tart gums and candies.
  • Run a humidifier in your bedroom overnight to keep the air moist.
  • Undergo regular preventive dental care (special toothpaste and fluoride applications may be recommended, too).
  • Use saliva substitutes, such as SalivaMAX.


If you have a thyroid disorder, you may also have dry mouth. If you're still learning about your thyroid problem, you may not have had time to make the connection. But the link exists because thyroid disease also means that the salivary gland produces and releases less saliva. And less saliva leads to dry mouth. Certain treatments for thyroid disorders can cause dry mouth, too. Some quick and easy remedies can make living with dry mouth more bearable.

A Word From Verywell

While having a dry mouth is an unpleasant effect of thyroid disease, it usually improves with treatment of hyperthyroidism or hypothyroidism. If you still have persistent problems even after your thyroid condition is adequately treated, some lifestyle modifications and over-the-counter remedies can ease your dry mouth.

5 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. Jung JH, Lee CH, Son SH, et al. High prevalence of thyroid disease and role of salivary gland scintigraphy in patients with xerostomia. Nucl Med Mol Imaging. 2017;51(2):169-177. doi:10.1007/s13139-016-0455-4.

  2. Agha-hosseini F, Shirzad N, Moosavi MS. Evaluation of xerostomia and salivary flow rate in Hashimoto's thyroiditis. Med Oral Patol Oral Cir Bucal. 2016;21(1):e1-5. doi:10.4317/medoral.20559

  3. Chandna S, Bathla M. Oral manifestations of thyroid disorders and its management. Indian J Endocrinol Metab. 2011;15(Suppl 2):S113-6. doi:10.4103/2230-8210.83343

  4. Klein hesselink EN, Brouwers AH, De jong JR, et al. Effects of radioiodine treatment on salivary gland function in patients with differentiated thyroid carcinoma: A prospective study. J Nucl Med. 2016;57(11):1685-1691. doi:10.2967/jnumed.115.169888

  5. National Institute of Dental and Craniofacial Research. Dry mouth.

Additional Reading

By Mary Shomon
Mary Shomon is a writer and hormonal health and thyroid advocate. She is the author of "The Thyroid Diet Revolution."