Thyroid disease and oral health.Dental professionals review and update their patients' medical histories at each appointment. Among the items on the complex list of medical health concerns is thyroid disease. Thyroid problems are very common, and because the thyroid gland affects almost every function of the body, dental professionals need to understand thyroid disease when treating affected patients.
As someone diagnosed with hypothyroidism caused by Hashimoto's disease, I am continually searching for evidence-based information and about thyroid conditions. There are books, articles, online communities, associations and foundations. New clinical conclusions are released weekly for this very complex disease.
Thyroid Disease in the United States
An estimated 27 million Americans have thyroid disease; more than half of them undiagnosed. Subtle changes in thyroid function can have significant health consequences. Women's risk of developing thyroid problems is seven times that of men. A family history of thyroid problems and increasing age affect the chances of a woman developing thyroid problems. A woman has almost a one-in-five chance of facing some type of thyroid disease in her lifetime. (1)
The history of thyroid disease can be traced back to when goiters were identified. (2) A goiter (struma) is a noncancerous enlargement or swelling of the thyroid gland. (1) The use of seaweed to treat goiter was first mentioned in 2700 BC, found among Emperor Shen Nung's prescriptions as part of the Pen Tsao, a treatise on herbal medicine first published in 1596). (2)
The thyroid gland is a butterfly-shaped gland at the base of the neck that produces several hormones. There are two main thyroid hormones produced. Thyroxine, otherwise called T4 (thyrogolobulin-4) because each molecule of hormone has four iodine atoms. Ninety-fine percent of the thyroid hormone in our circulation is T4. Most experts in thyroid disease believe that T4 is really only a precursor and a convenient way for the thyroid to store its hormone pool. T4 is the inactive hormone and is a reserve supply.
The other five percent of thyroid hormone is in the form of tri-iodothyronine or T3. T3 is the thyroxine molecule that has lost one iodine atom, due to the action of deiodinase, a de-iodinating enzyme. This allows T3 to be used for local tissue as the active hormone. A number of thyroid experts believe that T3 is the true thyroid hormone. T3 is much more powerful than T4 and is destroyed much more quickly. T3 only lasts a few hours; T4 lasts for days. Most of the T4 and T3 travel around the blood attached to a protein called thyroxine-binding globulin (TBG). The unattached hormone is free of the TBG and can also be measured as Free T4 and Free T3. All of the hormone together, both the free and that bound to TBG, are measured as Total T4 and Total T3. The pituitary gland produces TSH or thyroid-stimulating hormone. This hormone stimulates the thyroid gland to increase production. A high TSH determined by a blood test often means the thyroid is underactive and needs stimulation, while a low TSH can mean the thyroid is overactive. The thyroid gland is constantly reacting to changes in the levels of circulating TSH. Building the thyroxine molecule needs three components--iodine, thyroglobulin and thyroperoxidase. Iodine is a trace chemical element found in foods. Only tiny amounts of iodine are needed each day for thyroid function. The thyroid is efficient in taking iodine (in the form of iodide) up from the blood. There is normally thirty to forty times as much iodine in thyroid tissue as in the bloodstream. Inside the thyroid, the iodide meets up with thyroglobulin.
Thyroglobulin is the protein base upon which thyroine is synthesized. It is almost unique to the thyroid gland (some thyroglobulin is circulated in the blood). Thyroperoxidase causes iodine molecules to become attached to different sites on the thyroglobulin molecules, first making molecules that contain one, then two iodine atoms, which then double up to make a molecule containing four iodine atoms (T4). The thyroid gland receives signals from the pituitary gland and the hypothalamus. Cells in the hypothalamus respond to low levels of thyroxine in the blood by secreting thyrotropin-releasing hormone, (TRH) into special portals (modified blood vessels) in the pituitary stalk connecting to the pituitary gland. When the cells in the front section of the pituitary gland pick up these chemical messages, TSH is secreted into the bloodstream. The normal thyroid gland is constantly reacting to changes in the levels of circulating TSH. Thyroid problems can be caused by faulty TRH from the hypothalamus, faulty TSH secretion from the pituitary, lack of response to TSH, failure to produce thyroxine from the thyroid itself or if the thyroid becomes automonus (the whole gland or part of the gland producing thyroxine without regard to TSH changes). (1,3,4) The thyroid regulates the metabolism of our cells, our moods, emotions, cognition, appetite and behavior. (5,6)
If the thyroid excretes too much hormone, hyperthyroidism (overactive thyroid) results. The most common symptoms include nervousness, sweating, palpitations, nerve tingling, fatigue, and heat intolerance, hyperactivity, eye disorders and an increased appetite. Many autoimmune diseases can lead to hyperthyroidism when the immune system mistakenly attacks and destroys healthy body tissue. (7)
Autoimmune thyroid problems often lead to hyperthyroidism initially, followed by hypothyroidism (underactive thyroid) later in the disease process. This can result in Hashimoto's disease, a type of autoimmune thyroid disease in which the immune system attacks and destroys the thyroid gland. It is the most common form of hypothyroidism. (6) People with either Graves' disease (related to hyperthyroidism) (6) of hypothyroidism due to autoimmune problems are also at higher-than-normal risk of autoimmune diseases affecting other parts of the body. (3)
The most common symptoms of hypothyroidism are tiredness, feeling cold, constipation, hoarse voice, changes in hair and skin, heavy menstrual periods and weight gain. (8) The treatments for hyperthyroidism and hypothyroidism address the hormone imbalance. Options for treating Graves' disease range from administering antithyroid drugs to trying to destroy a significant portion of the gland with radioactive iodine or surgically removing a significant portion of the gland. Hypothyroidism is traditionally treated with synthetic T4. Some literature suggests that adding T3 can be beneficial because the body and mind depend on this most potent form of thyroid hormone, which is also the main form of the hormone that works in brain cells. (3,6)
Thyroid Cancer and Risk Factors
Thyroid cancer affects mainly younger people. Almost two of three cases are found in people between the ages of 20 and 55, and the survival rate is 97 percent. (9)
The causes of thyroid cancer include inadequate amounts of dietary iodine, a nutrient necessary for the thyroid to produce thyroid hormone. Another risk factor for thyroid cancer is exposure to radiation, whether during medical treatment or as radioactive fallout. Genetics and family history can also contribute to a higher risk of developing certain types of thyroid cancer. (1)
The Oral Health Care Provider's Responsibility
Dental personnel have a responsibility to conduct a thorough evaluation of the patient's health history to determine if their thyroid disease is being medically managed. Uncontrolled hyperthyroidism can put the dental patient at risk. Complications include the rare thyrotoxic crisis ("thyroid storm," a serious condition characterized by mental deterioration, high fever, extreme agitation and at times heart failure and jaundice). (6,10)
The use of epinephrine or other pressor ammines can cause a hypertensive crisis in a patient with uncontrolled hyperthyroidism. These patients can also be at risk for complications of hypertension, cardiac arrhythmias and congestive heart failure. (10) Patients with hypothyroidism need to be well controlled before having dental treatment. Patients with Hashimoto's thyroiditis may endure a short period of hyperthyroidism, and it may be best to avoid routine dental treatment during that acute period. Dental treatment modification may be necessary for dental patients under medical management and follow-up for a thyroid condition.
If a suspicion of thyroid disease arises for an undiagnosed patient, all elective dental treatment should be postponed until a complete medical evaluation is performed. (11) (A medically well-controlled patient will have no contraindications to have dental treatment. (10)
Thyroid Oral Implications
The common oral implications in hypothyroidism include macroglossia, dysgeusia, delayed eruption, poor periodontal health and delayed wound healing. A patient with hypothyroidism is susceptible to cardiovascular disease from arteriosclerosis and elevated LDL. (12) Consulting with the patient's primary care provider can give you the information needed to determine the patient's cardiovascular status.
Common oral findings in hyperthyroidism include increased susceptibility to dental caries, periodontal disease, enlargement of extraglandular thyroid tissue (mainly in the lateral posterior tongue), maxillary or mandibular osteoporosis, accelerated dental eruption and burning mouth syndrome. (13,14) Patients older than 70 are at risk for anorexia and wasting, atrial fibrillation and congestive heart failure. In younger patients, Graves' disease is the main manifestation. Middle-aged men and women most commonly have toxic nodular goiter. Graves' disease can also put a patient at a higher risk for connective-tissue diseases like Sjogren's syndrome and systemic lupus erythematosus. (11,15) There are no major side effects of thyroid replacement medication that affect the oral cavity. A common side effect of many medications is xerostomia. (14)
A thyroid nodule is thyroid tissue that has continued to grow. This nodule develops in the gland. The majority of the solid or fluid-filled lumps are noncancerous, and most nodules don't cause any symptoms. Only about five percent of thyroid nodules may be cancerous. Some thyroid nodules may become large enough to press on the windpipe or the esophagus, making it uncomfortable or difficult to swallow. (16)
If thyroid cancer is identified, treatment with large doses of radioactive iodine six weeks after the thyroid gland has been removed is required to remove any remaining cancerous tissue. Lifelong thyroid hormone replacement therapy is required after surgical removal of the thyroid gland. Surgery and radioactive iodine generally cure the cancer. (1)
Health Care Delivery and Other Concerns
Conducting an extraoral cancer examination for the thyroid is an important procedure for the dental professional to perform. The gland should first be inspected and then palpated; it is possible to palpate the gland standing in front of or behind the patient. Normal patients have thyroid glands that are difficult to feel. The dental professional should note any characteristics of the nodules or masses. (1)
Since the thyroid is the master gland of metabolism and energy, and problems with the gland affect factors including weight, mental health, fertility, heart disease risk, and many other important aspects of day-to-day health, it is important to protect this gland whenever possible. One way the dental professional can protect the thyroid gland is to use a thyroid collar when taking patient X-rays. The thyroid is extremely sensitive to radiation and excessive radiation exposure is a known risk factor for various thyroid conditions. (1)
It has been found that recent exposure to a surgical antiseptic that includes iodine (such as Povidone) can increase the risk of temporary thyroiditis, hypothyroidism or hyperthyroidism. Patients with underlying thyroid antibodies and a tendency toward autoimmunity appear to be at more risk. (1)
Too much soy protein in the diet has been shown to interfere with thyroid function only in patients who have hypothyroidism and are being treated with thyroid medications. (17) Human studies have shown no significant effect when soy is consumed in normal quantities.
Evidence supports the link between certain food groups with autoimmune disease of the thyroid that results in slowed metabolism. For example, gluten sensitivity or allergy can cause many different types of symptoms from migraines to fatigue to weight gain. (18)
Fluoride was used as a drug to treat hyperthyroidism because it makes the thyroid underactive quite effectively. This is due to the ability of fluoride to mimic the action of thyrotropin (TSH). Excess fluoride correlates with other thyroid-related issues such as iodine deficiency. Fluoride and iodine, both being members of the halogens group of atoms, have an antagonistic relationship. When there is excess of fluoride in the body it can interfere with the function of the thyroid gland. (1) Fluoride has been linked to thyroid problems. (19) Patients who wish to avoid the effect of fluoride on their thyroid can utilize a fluoride-free toothpaste such as Carifree, an oral neutralizer gel. (20)
Thiocyanate, one of the toxins contained in cigarettes, is especially dangerous to the thyroid gland in susceptible people. Cigarette smokers are also more likely to develop eye complications of Graves' disease. Patients who smoke increase their health risk by worsening their thyroid disease. (1)
Stress management plays a very important part in successful treatment of thyroid disease. Stress affects the thyroid gland negatively. Treating the thyroid without treating the stress can cause more problems. Incorporating regular relaxation exercise is critical to helping thyroid disease respond to the recommended medical treatment. (21)
It appears that in order to properly respond to thyroid disease treatment, several factors need to be considered. From medication to lifestyle, a patient challenged with thyroid disease can help their treatment be more effective and improve their well-being and quality of life. Dental professionals have a responsibility to be aware of the different dimensions of the disease and treatment that could affect a patient whose medical history reflects thyroid problems.
(1.) Thyroid disease information. About.com: thyroid. Available at http:thyroid.about.com.
(2.) American Thyroid Association Web site. Available at www. thyroid.org.
(3.) Smith T. How to cope successfully with thyroid problems. Lower Bourne, Farnham Surrey, Great Britain: Wellhouse Publishing Ltd.; 2001.
(4.) Thyroid Balance. Georgia Hormones Web site. Available at www.GeorgiaHormones.com.
(5.) Roizen M, Oz M. You: the owner's manual. New York: HarperResource; 2005.
(6.) Arem R. The thyroid solution. New York: Ballantine Books 1999.
(7.) Brownstein D. Overcoming thyroid disorders, 2nd ed. West Bloomfield, Mich.: Medical Alternatives Press; 2008.
(8.) Summaries for patients: comparison of two drug regimens for hypothyroidism. Annals of Internal Medicine Web site. Available at www.annals.org/cgi/content/summary/142/6/412.
(9.) Detailed Guicie: Thyroid Cancer. What are the key statistics about thyroid cancer? www.cancer.org.
(10.) Little J. Thyroid disorders. Part I, Part 2. Oral Surg Oral Med Oral Pathol Oral Radiol Endodontics 2006; 101(3): 276-84.
(11.) Pinto A, Glick M. Management of patients with thyroid disease. J Am Dent Assoc 2002; 133(7): 849-58.
(12.) Young ER. The thyroid gland and the dental practitioner. J Can Dent Assoc 1989:55:903-7.
(13.) Poumpros E, Logerb E, Engstrom C. Thyroid function and root resorption. Angle Orthod 1994: 64:389-94.
(14.) Burning Mouth Syndrome. Associated content Web site. Available at www.associatedcontent.com/article/106394/burning_mouth_syndrome_bms.html? cat=70.
(15.) Shomon M. Living well with autoimmune disease. New York: HarperCollins Publishers; 2002.
(16.) Oiseases and conditions: thyroid nodules. Mayo Clinic Web site. Available atwww.mayoclinic.com/health/thyroid-nodules/DS00491.
(17.) Persky VW, Turyk ME, Wang L et al. Effect of soy protein on endogenous hormones in postmeonopausal women. Am J Clin Nutr 2002; 75 (1):145-53; erratum in: Am J Clin Nutr 2002; 76 (3): 695.
(18.) Toscano V, Conti FG, Anastas E, et al. Importance of gluten in the induction of endocrine autoantibodies and organ dysfunction in adolescent celiac patients. Am J Gastroenterol 2000; 95(7): 1742-8.
(19.) Galletti PM, Joyet G. Effect of fluorine on thyroidal iodine metabolism in hyperthyroidism. J Clin Endocrinol Metab 1958); 18(10): 1102-10.
(20.) Carifree Web site. Available at www.carifree.com.
(21.) Hyman M. Ultra-Metabolism. New York: Atria Books; 2006.
By Sandi Roggow, RDH, BA
Sandi Roggow, RDH, BA, has been a clinical dental hygienist for 32 years working in Saginaw, Mich., and now Atlanta, Ga. She received her AAS from Kellogg Community College and her BA from Spring Arbor University and is a member of Sigma Phi Alpha, She is a business development and marketing consultant in the dental and media industries, She is currently developing www,thesmilemarket.com for sales of fun and innovative dental-related products. She can be contacted at firstname.lastname@example.org.