Find a Registered Dental Hygienist


Knowledge Network

FACT SHEET: Hyperthyroidism (also known as “thyrotoxicosis” and “overactive thyroid disease”; includes Graves’ disease [also known as “Graves-Basedow disease” and “Basedow’s disease”], toxic multinodular goitre [also known as “Plummer’s disease” and “Parry’s disease”], and several types of thyroiditis)

Date of Publication: January 27, 2017

Is the initiation of non-invasive dental hygiene procedures* contra-indicated?

  • No, assuming no recent treatment with radioactive iodine.

Is medical consult advised?  

  • Yes, if previously undiagnosed hyperthyroidism or enlarged thyroid gland is suspected1, in which case the patient/client should see his/her primary care physician.
  • Yes, if previously diagnosed hyperthyroidism is suspected to be undertreated (with manifest signs/symptoms of hyperthyroidism) or overtreated (with manifest signs/symptoms of hypothyroidism2), in which case the patient/client should see his/her primary care physician or endocrinologist. Even if the hyperthyroid patient/client is under good medical care, acute oral infection should also prompt consultation with patient/client’s physician.
  • Yes, if thyrotoxic crisis is suspected. Immediate medical assistance should be sought — this is a medical emergency. 
  • Yes, if patient/client taking antithyroidal thioamide drugs (such as carbimazole, methimazole, and propylthioruracil [PTU]) presents with fever, sore throat, or oral ulcerations. This may indicate agranulocytosis (i.e., dangerously low level of neutrophils, which are a type of white blood cells), which requires urgent medical care.
  • Yes, if patient/client is about to receive, or has recently received (within past week), radioactive iodine therapy, in order to clarify duration of restricted (1.83 m distance from other persons) period to minimize radiation risk to others, including the dental hygienist.

Is the initiation of invasive dental hygiene procedures contra-indicated?**

  • Possibly, depending on the certainty of diagnosis, level of disease control, and timing of radioactive iodine therapy.

Is medical consult advised? 

  • See above.

Is medical clearance required? 

  • Yes, if undiagnosed or severe hyperthyroidism is suspected.
  • Yes, if patient/client is taking antithyroidal thioamide drugs. These medications (particularly PTU) may rarely cause thrombocytopenia (low platelet count) or hypoprothrombinemia (low prothrombin level), both of which impair blood clotting, as well as leukopenia (low white blood cell count), which increases risk of serious infection. A physician can order blood tests (e.g., platelet count, prothrombin time, and white blood cell count) to rule out the presence of these complications. PTU may also increase the anticoagulant effects of warfarin, which is commonly used in the management of atrial fibrillation.

Is antibiotic prophylaxis required?  

  • No.

Is postponing treatment advised?

  • Yes, if patient/client has very recently been treated with radioactive iodine (which is usually administered as one oral dose) in order to protect the dental hygienist, other staff, and patients/clients from radiation exposure. Depending on the dose of I131 given, duration of postponement should be 1 to 3 days post-administration for non-pregnant oral healthcare providers and 1 to 5 days for pregnant oral healthcare providers3. Patients/clients treated with I131 should maintain a distance of at least 1.83 metres (6 feet) from other persons during the restricted period. 
  • Yes, if hyperthyroidism is suspected in an undiagnosed or untreated patient/client; a complete medical evaluation is indicated before commencement of invasive procedures.
  • Yes, if severe, poorly controlled hyperthyroidism is suspected (in order to avoid risk of thyrotoxic crisis); such patients/clients should be referred for urgent medical care, with dental hygiene care postponement until the underlying metabolic disturbance has been corrected.
  • Yes, if cardiovascular signs/symptoms (e.g., chest pain, palpitations) occur in the course of dental hygiene treatment; conditions such as angina pectoris are exaggerated in thyrotoxicosis. The management protocol for the specific situation should be followed. 
  • In general, the patient/client with mild symptoms of untreated hyperthyroidism (often passing as acute anxiety) is not in danger when receiving dental hygiene therapy, and the well-managed (euthyroid) patient/client requires no special regard. 

Oral management implications

  • Palpation of the thyroid gland should be part of the head and neck examination by the dental hygienist. Diffuse enlargement or nodules may be detected.
  • Patients/clients with a history of hyperthyroidism should be queried regarding the presence of cardiovascular disease.
  • Blood pressure should be monitored, because it may be elevated in patients/clients with poorly controlled disease.
  • Stress management and brief appointments are important for patients/clients with poorly controlled disease to minimize risk of precipitating a thyrotoxic crisis. 
  • Patients/clients with untreated or partially treated hyperthyroidism are very sensitive to the effects of epinephrine or other sympathomimetics. Their use is contraindicated until good medical management is implemented. Improper use can cause the patient/client to experience a hypertensive crisis, tachycardia, and/or dysrhythmia.
  • Nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin, can increase the amount of circulating thyroid hormone, making control of hyperthyroidism more difficult.
  • Thyrotoxic crisis — a medical emergency — may be precipitated by trauma, infections, and surgical procedures in untreated or poorly treated patients/clients with severe hyperthyroidism.
  • Development of autoimmune connective tissue diseases such as Sjögren’s syndrome and systemic lupus erythematosus should be considered when evaluating the patient/client who has a history of Graves’ disease.

Oral manifestations

  • Mild tremor of the tongue is common.
  • Increased susceptibility to caries, periodontal disease, enlargement of extraglandular thyroid tissue (mainly lingual thyroid tissue on the posterior dorsal tongue), osteoporosis of alveolar bone (and entirety of mandible and maxilla), and burning mouth syndrome are less common manifestations. 
  • In children, the teeth and jaw develop quickly. Premature loss of deciduous teeth and accelerated eruption of permanent teeth are common.
  • Lingual thyroid4 may uncommonly be a cause of thyrotoxicosis. This rare condition manifests orally as a nodule at the base of the tongue. Dysphagia, dysphonia, bleeding, and upper respiratory tract obstruction may occur. 
  • Sialolith formation may be induced by the antithyroid drug propylthioruracil (PTU).
  • Decreased sense of taste may infrequently result from antithyroid drugs such as PTU and methimazole.
  • Salivary gland swelling and pain, as well as loss of taste, are acute risks of radioactive iodine therapy. Longer term complications are hyposalivation, xerostomia, mouth pain, recurrent sialoadenitis, and caries.

Related signs and symptoms

  • Hyperthyroidism is characterized by an excess of thyroid hormone5 in the bloodstream, usually resulting from an overactive thyroid gland. Causes of hyperthyroidism include Graves’ disease6; congenital hereditary goitre7; functional ectopic thyroid tissue; multinodular goitre; thyroid adenoma (a benign tumour of the thyroid gland); ingestion of thyroid hormone (thyrotoxicosis factitia) or thyroid-active agents (e.g., iodocasein for weight reduction); pituitary disease; and subacute painful and subacute painless (postpartum) thyroiditis (each of which has a transient hyperthyroidism phase). In rare cases, metastases of follicular carcinoma of the thyroid gland can cause thyrotoxicosis.
  • Although less common than hypothyroidism, hyperthyroidism exhibits a similar female preponderance — by an 8:1 female-to-male ratio. By far, Graves’ disease is the most common cause of hyperthyroidism in Canada; it occurs in nearly 2% of women and 0.2% of men, usually presenting between 20 and 50 years of age.
  • Diffusely enlarged goitre usually accompanies Graves’ disease. Palpable nodules (which secrete excessive amounts of thyroid hormone) are present in the less common toxic multinodular goitre. 
  • Direct and indirect effects of excessive thyroid hormone (which increases metabolic activity) cause the clinical picture in Graves’ disease and other thyrostimulatory disorders. Common signs/symptoms are nervousness, irritability, restlessness, insomnia, emotional lability, fatigue (associated with general muscle weakness), tachycardia (abnormally rapid resting heart beat), palpitations, elevation of blood pressure (systolic more than diastolic), heat intolerance, and weight loss.
  • Patients/clients find it difficult to sit still, are continually moving, and often have a tremor of the hands and of closed eyelids. In younger patients/clients, common findings are short attention span and weight loss despite an increased appetite. In females, menstruation tends to be decreased. 
  • The patient/client’s skin is warm and moist, and the complexion is rosy. Frequent blushing and hyperhidrosis (profuse sweating) are common. Excessive melanin pigmentation of the skin (but not of the oral mucosa) and palmar erythema may be present. Hair becomes fine and friable, and the nails soften.
  • Atrial fibrillation8 is rare in persons under 50 years of age, but occurs in about 20% of older patients/clients with Graves’ disease. Heart failure (HF) may occur, as may dyspnea (shortness of breath) unrelated to HF, which instead is related to weakness of the respiratory muscles.
  • Ophthalmopathy is seen in 50% of patients/clients with Graves’ disease, and is linked to an eye-specific autoimmune process. Its features are periorbital edema and inflammation of the extraoccular muscles, in addition to an increase in orbital connective tissue and fat. This results in eyelid retraction, lid lag on blinking, chemosis (conjunctival swelling), and unilateral or bilateral exophthalmos (abnormal protrusion of the eyeball). Disease progression may lead to double vision and loss of vision secondary to compressive optic neuropathy or exposure keratopathy. Unlike many complications of Graves’ disease, exophthalmos is usually irreversible even after antithyroid treatment.
  • Thyrotoxic patients/clients often show eye signs unrelated to Graves’ ophthalmopathy. These signs — related to overstimulation of the sympathetic nervous system — include infrequent blinking, stare with widened palpebral fissures, jerky eyelid movement, and failure to wrinkle the brow on upward gaze.
  • If left untreated, hyperthyroidism may lead to thyrotoxic crisis (thyroid storm), a rare life-threatening medical emergency heralded by the onset of nausea, vomiting, anorexia, abdominal pain, and extreme restlessness. High fever, profuse sweating, marked tachycardia, cardiac arrhythmias, heart failure, pulmonary edema, and delirium soon develop, followed by stupor, coma, severe hypotension, and death if untreated. Nearly all persons who develop thyrotoxic crisis have long-standing hyperthyroidism, with goitre, eye signs, and wide pulse pressure9.
  • Dermopathy occurs in fewer than 2% of patients/clients with Graves’ disease. This manifests as nonpitting edema, usually over the anterolateral aspects of the tibia (shin). In chronic cases, discrete nodules and plaques can be seen.
  • Thyroid acropachy is a rare complication of Graves’ disease. This condition is characterized by clubbing and soft tissue swelling of the distal phalanx of the fingers and toes, often with discolouration and thickening of the overlying skin. 
  • Glucose intolerance and, more rarely, diabetes mellitus may occur with hyperthyroidism. Other metabolic effects include increased bone loss (osteoporosis), which may be seen in radiographs.
  • Risk of death from thyroid cancer, and possibly several other cancers, is slightly increased if hyperthyroidism is treated with radioactive iodine.

References and sources of more detailed information

Date: October 10, 2016
Revised: July 6, 2021


1 Diagnostic tests for hyperthyroidism include serum measurement of thyroid-stimulating hormone (TSH; also known as thyrotropin), thyroid hormone, and thyroid binding globulin (TBG), and, less commonly, administration of radioactive iodine to measure uptake by the thyroid gland (RAIU). Treatment may involve antithyroid drugs (including propylthiouracil, methimazole, and carbimazole) that interfere directly with thyroid hormone synthesis, radioactive iodine, or subtotal thyroidectomy. The adrenergic component in thyrotoxicosis can be managed with β-blocker drugs such as propranolol.
2 Signs/symptoms of decreased thyroid activity include cold intolerance, dry skin, fatigue, poor memory retention, and weight gain despite decreased appetite.
3 I131 concentrations are present in the saliva for as long as 7 days post-administration.
4 Lingual thyroid is a rare condition of the oropharyngeal region caused by failure in descent of the thyroid gland to its normal position during embryogenesis. The ectopic thyroid tissue results in an abnormal mass at the base of the tongue. Patients/clients with lingual thyroid or other ectopic thyroid tissue are more likely to have hypothyroidism than hyperthyroidism. It is important that assessment by a physician occur before removal of a lingual thyroid mass, because it may be the only source of thyroid hormone in the patient/client.
5 Thyroid hormone is a collective term for thyroxine (T4) and triiodothyronine (T3), both of which are secreted by the thyroid gland. T4 is converted to T3 in the peripheral tissues.
6 Graves’ disease is an autoimmune disorder, in which stimulatory antibodies lead to an overactive thyroid gland.
7 Goitre is generalized enlargement of the thyroid gland, and may be either diffuse or nodular.
8 Atrial fibrillation is an arrhythmia in which the heart’s two upper chambers (atria) beat irregularly and out of coordination with the two lower chambers (ventricles). Treatment is important to prevent stroke and improve quality of life.
9 Pulse pressure is the difference between systolic blood pressure (SBP) and diastolic blood pressure (DBP). For example, if BP is 120/80 mmHg, then pulse pressure is 40.

* Includes oral hygiene instruction, fitting a mouth guard, taking an impression, etc.
** Ontario Regulation 501/07 made under the Dental Hygiene Act, 1991. Invasive dental hygiene procedures are scaling teeth and root planing, including curetting surrounding tissue.