How Thyroid Disease Causes Dry Mouth

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Thyroid disease can cause 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 bring about xerostomia. Dry mouth is not life-threatening, but it, among other things, can make swallowing difficult, cause bad breath, and even lead to complications like cavities and oral infections.

thyroid and dry mouth
Verywell / Gary Ferster


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

This is believed to be related to slowed metabolism associated with a hypothyroid disease. Untreated or partially treated hyperthyroidism can cause dry mouth as well, though the reason is not clear.

Thyroid Conditions

While dry mouth is usually 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: A common type of hyperthyroidism, Grave's disease causes weight loss, hyperactivity, and insomnia, and well as dry mouth.


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

  • Radiation therapy: Radiation, which is often used for the treatment of thyroid cancer, can affect the thyroid glands and may damage the salivary glands, diminishing the amount of saliva in the mouth.
  • Radioiodine therapy: Radioiodine is used for the treatment of 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 instances, excessive thyroid hormone replacement can also cause dry mouth.


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

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

*With severe cases of dry mouth

While everyone gets a dry mouth now and then, when it lasts for several weeks, it may be a symptom of thyroid disease or another underlying health problem. If you notice that you have had a persistent sensation of dry mouth, you should talk to your doctor.


Besides getting the right treatment for your thyroid disease (one that controls your condition, as well as its side effects), there are some other approaches to easing a dry mouth. Often, using these simple strategies along with your thyroid treatment can help you feel more comfortable and prevent the complications of dry mouth.

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

A Word From Verywell

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

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  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. Reviewed July 2018.

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