Dry mouth, also known as xerostomia, occurs due to absent or reduced saliva flow.
Xerostomia isn't a disease per se, but it is a symptom of a number of medical conditions.
Thyroid diseases are accompanied by a wide range of symptoms, and in this article, we’re going to explore whether conditions affecting the thyroid gland could also cause dry mouth.
Causes of dry mouth
Saliva has an important role in our dental health. It limits the growth of bacteria, washes away food particles, and prevents the decay of teeth.
Additionally, saliva increases our ability to taste the food we eat, and it also helps us chew and swallow. We tend to think that the process of digestion starts in the stomach, but actually it starts in your mouth due to the fact that saliva contains enzymes which participate in breaking down the food we eat.
Dry mouth is a problem that’s usually ignored. Most people don’t pay too much attention to dry mouth until the problem aggravates.
Xerostomia can range from mild to severe in intensity and affect a person’s quality of life. Causes of xerostomia are numerous, and they include the following:
- Cancer treatments such as chemotherapy and radiotherapy
- Exercising or playing in the heat
- Injury or surgery
- Medications including many over-the-counter medications, hypertensive drugs, muscle relaxants, antidiarrheals, urinary continence drugs, many antidepressants, and Parkinson’s disease drugs
- Older age; while xerostomia isn’t a natural part of aging many older people have dry mouth due to medications they take
- Smoking or chewing tobacco
- Snoring and sleeping with mouth open
- Some health conditions and illnesses such as anxiety disorders, HIV/AIDS, depression, stroke, Alzheimer’s disease, poorly managed diabetes, Parkinson’s disease, Sjogren’s syndrome (dry mouth and dry eyes)
Does thyroid disease cause xerostomia
As seen above, xerostomia can occur due to a number of reasons. If you have dry mouth quite frequently, it's useful to schedule an appointment to see the doctor because, in most cases, it's a result of some underlying health problem.
But, is thyroid disease one of those underlying health conditions that contribute to xerostomia?
Jung et al. carried out a study whose main objective was to estimate the prevalence of thyroid diseases in subjects with xerostomia. They discovered that more than half of patients with xerostomia also had thyroid disease.
More precisely, 53.2% of people with xerostomia also had thyroid disease, but 38% had thyroid disease alone.
Of patients with thyroid disease, 30.4% had Hashimoto’s thyroiditis, 10.1% had subacute thyroiditis, 2.5% had subclinical hypothyroidism, and 1.3% had Graves’ disease[i].
How thyroid disease leads to dry mouth
A growing body of evidence has confirmed that thyroid disease contributes to xerostomia or dry mouth.
But, you’re probably wondering how and why it happens.
Thyroid diseases affect salivary function through various mechanisms.
Patients with thyroid disease exhibit periepithelial lymphocytic infiltration (benign accumulations of lymph cells in the skin) and oligoclonal B-cell expansion similar to patients with Sjogren’s syndrome, the extrathyroidal manifestation of thyroid diseases could affect salivary function directly.
Also, thyroid disease can influence salivary function when patients affected by these conditions develop Sjogren’s syndrome.
A study which confirmed that Hashimoto's thyroiditis is strongly associated with dry mouth also showed that autoimmune changes in endocrine glands like the thyroid might also occur in exocrine glands like a salivary gland. The process of both types of glands is secretion, and it may explain why people with Hashimoto's thyroiditis develop xerostomia. Basically, autoimmunity can cause changes in salivary flow rate.
Although multiple mechanisms play a role in the relationship between thyroid diseases such as Hashimoto's thyroiditis and dry mouth, they are still poorly understood. One mechanism of action could be related to cytokines.
Exposure of salivary glands to pro-inflammatory cytokines interferes with their ability to make saliva. As you're already aware, Hashimoto's thyroiditis is an autoimmune condition, and it is involved with inflammation.
The good news is that stimulated salivary flow rate is not significantly diminished in Hashimoto’s thyroiditis meaning salivary stimulation may aid management of xerostomia in these patients[ii].
Autoimmune conditions affecting the thyroid, such as Hashimoto’s, can go hand in hand with Sjorgren’s syndrome. Screening patients with autoimmune thyroiditis for Sjogren’s syndrome and vice versa is important in order to identify and manage xerostomia.
A reminder – Sjogren’s syndrome is one of the biggest causes of dry mouth. Autoimmune thyroiditis and Sjogren’s syndrome share some pathogenic mechanisms[iii] which could be yet another way through which thyroid conditions cause xerostomia.
Symptoms of xerostomia
The biggest reason people don’t really go to the doctor’s for xerostomia is that they believe it’s not a big deal that their mouth is dry. Only when problem aggravates do we realize consulting a doctor is important. Xerostomia is indicated by various symptoms such as:
- Bad breath
- Changed sense of taste
- Difficulty speaking, chewing and swallowing
- Dryness or feeling of stickiness in the mouth
- Grooved or dry tongue
- Lipstick sticking to the teeth in women
- Problems wearing dentures
- Sore or dry throat and hoarsenes
- Thick and stringy saliva
Dry mouth may also be associated with the following[iv]:
- Cheilitis or inflammation and fissuring (cracking and splitting) of the lips
- Fungal infections in the mouth e.g., thrush
- Increased need to drink water, especially at night
- More frequent gum disease
- More plaque and tooth decay
- Painful tongue
- Salivary gland infection
How is dry mouth treated?
You should see the healthcare provider who will recommend the best treatment option.
Generally speaking, the treatment of dry mouth depends on various factors, including the underlying disease. Managing the underlying condition can help improve salivary flow.
Therefore, if thyroid diseases are to blame for your xerostomia, then improving the function of the thyroid gland could also help improve salivary flow and tackle dryness in your mouth.
In cases when dry mouth is caused by specific medications, the doctor either alter the dosage or prescribes different drugs.
Another treatment method for dry mouth is to stimulate the production of saliva. Basically, the doctor prescribes medications that promote salivary flow. As seen above in the article, stimulating production of saliva can be beneficial for patients with Hashimoto’s thyroiditis.
Due to the fact that dry mouth can lead to tooth decay and other problems in the oral cavity, your doctor will recommend adequate treatment measures to protect your teeth. For example, in order to protect cavities, the dentist may fit you for fluoride trays. You need to fill these trays with fluoride and wear over the teeth at night.
Tips for managing dry mouth
In addition to doctor-recommended treatment that you need to follow in order to manage xerostomia, there are many other things you can do.
Like many other conditions and problems affecting our body, dry mouth also requires certain changes in our lifestyle. To overcome dry mouth and complications it could cause (because saliva is important) you may want to try the following[v]:
- Drink plenty of water – the reality is that we don’t drink enough water although it’s vital for our health and wellbeing. Ideally, you should drink sips of water throughout the day. Make sure you drink between eight to 12 glasses of water every day, but if you tend to forget to drink water regularly you can always set up a reminder on your phone or write it down on post-it note
- Suck on hard candy or chew gum – this isn’t an excuse to eat sweet and sugar-laden candies or chew gums you loved in childhood. Opt for sugar-free alternatives of hard candies and gums as they’ll help promote salivary flow without negatively affecting your teeth
- Limit alcohol, consumption of coffee and acidic juices – all these beverages could contribute to the drying effect and make the problem worse. That’s why it’s better to avoid them entirely or reduce their intake. Read product labels to avoid consuming products with hidden alcohol
- Brush teeth after each meal – when you have dry mouth, it's easier for bacteria to spread and cause gum disease and other problems. Dry mouth also paves the way to cavities. For those reasons, it's useful to brush teeth after each meal. Soften the toothbrush in a cup of warm water, so it's gentler on your gums. Consult your dentist about using a fluoride rinse
- Use a humidifier at night – sleeping with mouth open can also cause or worsen dry mouth. It’s practical to use a humidifier at night, especially during winter. A humidifier will moisten the room and make it easier for you to sleep and you won’t wake up with dry mouth in the morning
- Avoid tobacco – smoking or chewing tobacco is an unhealthy habit that increases the risk of various health problems, and xerostomia is one of them. As seen above in the article, tobacco use is one of the most common causes of dry mouth. Therefore, you should avoid smoking cigarettes or chewing tobacco to protect your mouth and overall health for that matter
- Moisten food – in people with dry mouth salivary glands don’t produce enough saliva and it can be difficult to chew and swallow food, especially when it’s dry. To avoid that issue, you may want to moisten dry foods with sauces, milk, broth, or melted butter. That way, it will be easier to chew food and swallow it afterward
- Moisturize your lips – get a good lip balm to soothe cracked lips, a common problem associated with dry mouth
- Breathe through your nose – try to breathe through your nose and not your mouth. That way, air flow will not aggravate dry mouth
- Try using over-the-counter saliva substitutes – find products containing xylitol or hydroxyethyl cellulose. As saliva substitutes, these products would make it easier for you to eat food, and they could also prevent tooth decay
- Avoid products such as over-the-counter antihistamines and decongestants – they worsen dry mouth
- Avoid spicy and salty foods – they cause irritations. Dry mouth makes oral cavity sensitive and more prone to irritations and inflammation, the last thing you want
Dry mouth or xerostomia is a common problem that occurs as a symptom of an underlying health condition rather than a standalone disease.
Multiple health problems can cause dry mouth, and thyroid diseases are not exceptions. Studies have shown that autoimmune conditions such as Hashimoto’s thyroiditis and Graves’ disease can lead to dry mouth.
People with hypo- and hyperthyroidism can also develop this problem. Mechanisms of action are numerous, but more studies are necessary to elucidate them all.
Treatment of underlying condition, in this case, thyroid disease, can aid treatment of dry mouth.
[i] Jung, J. H., Lee, C. H., Son, S. H., Jeong, J. H., Jeong, S. Y., Lee, S. W., … Ahn, B. C., (2017). High Prevalence of Thyroid Disease and Role of Salivary Gland Scintigraphy in Patients with Xerostomia. Nuclear medicine and molecular imaging, 51(2), 169–177. doi:10.1007/s13139-016-0455-4. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5429303/
[ii] Agha-Hosseini, F., Shirzad, N., & Moosavi, M. S. (2015). Evaluation of Xerostomia and salivary flow rate in Hashimoto's Thyroiditis. Medicina oral, patologia oral y Cirugia buccal, 21(1), e1–e5. doi:10.4317/medoral.20559. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4765761/
[iii] Baldini, C., Ferro, F., Mosca, M., Fallahi, P., & Antonelli, A. (2018). The Association of Sjögren Syndrome and Autoimmune Thyroid Disorders. Frontiers in Endocrinology, 9, 121. doi:10.3389/fendo.2018.00121. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5891591/
[iv] Everything you need to know about dry mouth, Medical News Today. Retrieved from: https://www.medicalnewstoday.com/articles/187640.php
[v] eight tips to relieve your dry mouth, Cleveland Clinic. Retrieved from: https://health.clevelandclinic.org/8-tips-to-relieve-your-dry-mouth/