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CDHO Advisory: Hypothyroidism









Use of the dental hygiene interventions of scaling of teeth and root planing including curetting surrounding tissue, orthodontic and restorative practices, and other invasive interventions for persons1 with hypothyroidism.


Cite as College of Dental Hygienists of Ontario, CDHO Advisory Hypothyroidism, 2021-07-06


Scaling of teeth and root planing including curetting surrounding tissue, orthodontic and restorative practices, and other invasive interventions (“the Procedures”).





Advanced practice nurses
Dental assistants
Dental hygienists
Health professional students
Public health departments
Regulatory bodies


To guide dental hygienists at the point of care relative to the use of the Procedures for persons who have hypothyroidism, chiefly as follows.

  1. Understanding the medical condition.
  2. Sourcing medications information.
  3. Taking the medical and medications history.
  4. Identifying and contacting the most appropriate healthcare provider(s) for medical advice.
  5. Understanding and taking appropriate precautions prior to and during the Procedures proposed.
  6. Deciding when and when not to proceed with the Procedures proposed.
  7. Dealing with adverse events arising during the Procedures.
  8. Record keeping.
  9. Advising the patient/client.


Child (2 to 12 years)
Adolescent (13 to 18 years)
Adult (19 to 44 years)
Middle Age (45 to 64 years)
Aged (65 to 79 years)
Aged, 80 and over
Parents, guardians, and family caregivers of children, young persons and adults with hypothyroidism.


For persons who have hypothyroidism: to maximize health benefits and minimize adverse effects by promoting the performance of the Procedures at the right time with the appropriate precautions, and by discouraging the performance of the Procedures at the wrong time or in the absence of appropriate precautions.



Nomenclature of hypothyroidism

Resources consulted

  1. Adult hypothyroidism, alternative name for hypothyroidism.
  2. Borderline hypothyroidism, also called compensated hypothyroidism, a common condition that cannot be accurately diagnosed clinically without blood tests, in which the
    1. thyroid-stimulating hormone is elevated
    2. thyroid hormone levels are normal or only slightly subnormal.
  3. Congenital hypothyroidism, also called neonatal hypothyroidism, a condition in infancy or early childhood induced by genetic or environmental factors, in which in-utero thyroid hormone deficiency results from 
    1. missing thyroid
    2. faulty development of the thyroid during pregnancy
    3. development of the thyroid in the wrong anatomical place which thus fails to function.
  4. Cretinism, a congenital condition also called congenital myxedema, cretinoid dysplasia
    1. caused by thyroid hormone deficiency during fetal development
    2. characterized in childhood by 
      1. dwarfed stature
      2. mental retardation
      3. dystrophy of the bones
      4. low basal metabolism. 
  5. Goiter, also called goitrous hypothyroidism or compensatory goiter, in which the thyroid is enlarged because of constant stimulation. 
  6. Hashimoto thyroiditis, also called autoimmune thyroiditis, the most common cause of hypothyroidism, an autoimmune disorder in which thyroid cells are destroyed by various cell-mediated and antibody-mediated immune processes.
  7. Hyperthyroidism, (CDHO Advisory) a condition which
    1. is caused by overproduction of thyroid hormone 
    2. raises thyroid hormone in the blood to excessive levels, which adversely affects various tissues of the body
    3. causes an abnormally increased rate of metabolism.
  8. Hypothyroidism, a condition in which the body lacks thyroid hormones
  9. Myxedema, also called advanced hypothyroidism, is
    1. caused by decreased activity of the thyroid in adults
    2. characterized by dry skin, swellings around the lips and nose, mental deterioration, and a subnormal basal metabolic rate
    3. rare but may be life-threatening; the most severe form, called myxedema coma, is a medical emergency.
  10. Neonatal hypothyroidism, decreased or, rarely, absent thyroid hormone production. 
  11. Postpartum thyroiditis, also called subacute thyroiditis, a transient form of hypothyroidism
  12. Secondary hypothyroidism, the thyroid is normal but not producing enough hormones because of a problem in the pituitary or hypothalamus.
  13. Thyroid gland, makes and stores hormones that help regulate the heart rate, blood pressure, body temperature, and metabolism.
  14. Thyroid hormone deficiency, the consequence of hypothyroidism.
  15. Thyroid hormones
    1. are controlled by the hypothalamus which, according to the blood level of thyroxine and triiodothyronine, stimulates the pituitary to produce thyroid-stimulating hormone, which regulates the thyroid’s production of thyroid hormones
    2. include
      1. thyroxine, which
        1. is the body’s main metabolic hormone
        2. regulates 
          1. the rate of oxygen use by cells
          2. the generation of body heat 
        3. promotes glucose metabolism 
      2. free thyroxine, which is 
        1. the amount of the free (unbound) active thyroxine circulating in the blood
        2. measured by specific laboratory procedures
      3. triiodothyronine, which
        1. is the most active thyroid hormone and affects all body processes
        2. helps regulate growth and development
        3. helps control metabolism and body temperature
        4. by negative feedback, acts to inhibit the secretion of thyroid- stimulating hormone by the pituitary gland
        5. circulates in blood almost completely bound to carrier proteins
      4. free triiodothyronine, the free (unbound) portion of triiodothyronine, that is believed responsible for the biological action 
      5. calcitonin, which regulates the amount of calcium in the blood.
  16. Thyroiditis, inflammation (not infection) of the thyroid, of which there are several types.

Overview of hypothyroidism


  1. affects 
    1. women most commonly 
      1. especially in the age range above 50
      2. as many as ten percent have some degree of thyroid hormone deficiency
    2. adults generally
    3. children, including babies and teenagers
    4. about two percent of the population
    5. many or even all body functions 
  2. affects reproduction and pregnancy
    1. is the most common thyroid disorder occurring before, during or after pregnancy 
    2. may occur because of the development during pregnancy of antibodies that neutralize the woman’s thyroid
    3. impairs fertility through
      1. interference with ovulation resulting from low levels of thyroid hormone
      2. autoimmune disorder, which also may be linked to the hypothyroidism
      3. menstrual irregularities, such as
        1. heavy periods
        2. amenorrhea 
      4. decreased libido 
    4. if left untreated is linked to 
      1. increased incidence of birth defects
      2. lower IQs in neonatal hypothyroidism
      3. miscarriage 
      4. preeclampsia
      5. premature delivery
    5. may be overlooked because of confusion with common conditions in pregnancy, such as
      1. fatigue
      2. excessive weight gain
    6. may be treated with synthetic hormones, which
      1. are generally considered safe because the chemical structure is nearly identical to that of the natural hormones
      2. may require the dose to be increased during pregnancy for women with previously treated hypothyroidism
  3. is caused by 
    1. defects in the thyroid arising from or associated with
      1. autoimmune disorders, such as
        1. Hashimoto thyroiditis, autoimmune thyroiditis, which
          1. is a common thyroid gland disorder
          2. occurs at any age, but is most often seen in middle-aged women, especially with a family history of the disease
          3. is caused by a reaction of the immune system against the thyroid gland
          4. affects between 0.1 and 5 percent of all adults in Western countries
        2. thyroiditis, which may have causes other than autoimmune disorder
        3. type I diabetes (CDHO Advisory), in association with which
          1. hypothyroidism occurs more commonly in women than men
          2. hypothyroidism seems to be particularly common in teenage girls
      2. medical conditions 
        1. goitrous hypothyroidism
        2. atrophic thyroid, small thyroid
        3. birth defects
    2. side-effects of treatment
      1. surgery for
        1. hyperthyroidism (CDHO Advisory)
        2. cancer of the thyroid
        3. other conditions of the thyroid involving removal of all or part of the thyroid 
        4. cancer of the head and neck involving surgery with or without radiation exposure to the neck
      2. radiation of the
        1. thyroid
        2. head and neck
      3. medications
        1. specific medications
        2. radioactive iodine used in the treatment of hyperthyroidism
    3. diet
      1. iodine deficiency
      2. iodine excess
    4. abnormalities of the pituitary or hypothalamus, in which 
      1. pituitary does not release enough hormone to stimulate the thyroid, possibly because of a benign tumour
      2. disorder of the hypothalamus
  4. seldom creates problems in the early stages but the slowing of metabolism over time, if untreated, may result in 
    1. medical conditions or complications, such as 
      1. obesity
      2. joint pain
      3. heart disease
    2. non-specific symptoms and signs in various systems
      1. general
        1. fatigue
        2. weakness
        3. sluggishness
        4. intolerance to cold 
        5. poor appetite
        6. puffiness of the face
        7. constipation
        8. weight gain, likely because of some combination of
          1. fluid retention
          2. reduced ability to burn calories
          3. increased levels of hormones that drive hunger
          4. difficulty losing weight
      2. mental health conditions
        1. difficulty concentrating
        2. memory impairment
        3. depression 
        4. sleep disorders
        5. irritability
      3. musculature 
        1. aches
        2. tenderness
        3. stiffness
        4. cramps
        5. weakness
      4. joints 
        1. pain
        2. stiffness
        3. swelling
      5. skin and hair
        1. pale, cold, dry, coarse, rough or scaly skin
        2. thickening of the skin and underlying tissues, myxedema
        3. hair
          1. coarse, dry, brittle 
          2. lost
        4. brittle fingernails
      6. hoarseness of voice
      7. changes in cholesterol levels that increase the risk of heart disease, primarily because an underactive thyroid may raise the level of low-density lipoprotein (LDL) cholesterol
    3. specific signs
      1. absence of thyroid on palpation
      2. slow reflexes
      3. slow heart rate
  5. occurs in children, including babies and teenagers
    1. infants born with neonatal hypothyroidism  owing to absence or dysfunction of the thyroid 
      1. at birth 
        1. may show few indications, which is why routine thyroid screening is advocated for newborns 
        2. or may exhibit
          1. jaundice
          2. frequent choking
          3. large, protruding tongue
          4. puffiness of the face
      2. with the progression of the hypothyroidism, are likely to be subject to
        1. feeding problems
        2. failure to grow and develop normally 
        3. constipation
        4. poor muscle tone
        5. excessive sleepiness
    2. older children may variously exhibit the signs and symptoms that occur in adults, plus
      1. delayed deciduous dentition (see oral health considerations)
      2. dwarfism
      3. yellow, dry, thick skin
      4. obesity, to some degree
      5. thick lips and tongue
      6. short hands with thick fingers
      7. mental retardation
      8. delayed puberty
      9. slow movement 
  6. is associated with risk factors, including
    1. female gender
    2. age over 50 years; increased in the elderly
    3. previous radiation treatment to the neck or upper chest 
    4. obesity
    5. thyroid surgery
    6. a close relative, such as a parent or grandparent, with an autoimmune disease
    7. previous treatment with radioactive iodine or anti-thyroid medications
    8. untreated thyroid disease in mothers, which increases the risk of birth defects in their babies: the prognosis is good for the baby if the condition is detected within the first few months of life
  7. is diagnosed by accurate thyroid function tests, specifically with
    1. thyroid-stimulating hormone, which
      1. provides an important initial screening test
      2. provides an important test for the confirmation of borderline hypothyroidism (i.e., subclinical hypothyroidism) for which diagnosis is otherwise extremely difficult because
        1. symptoms may be vague or absent
        2. once treatment is started it usually continues for life and is difficult to stop
    2. thyroid hormones, when showing low levels of thyroxine and triiodothyronine in the blood
  8. is treated with synthetic thyroid hormones, which are usually simple, safe and effective once the appropriate dosage is established
  9. usually progresses if left untreated, which may result though rarely in severe
    1. life-threatening depression (CDHO Advisory)
    2. heart disease
    3. myxedema coma.

Multimedia and images

Comorbidity, complications and associated conditions

Comorbid conditions are those which co-exist with hypothyroidism but which are not believed to be caused by it. Complications and associated conditions are those that may have some link with it. Distinguishing among comorbid conditions, complications and associated conditions may be difficult in clinical practice.

Resources consulted

  1. Mental health conditions are associated with hypothyroidism even though most hypothyroid patients do not meet the criteria for a mental disorder; the associated conditions include
    1. diminished cognition, slow thought process, slow motor function, and drowsiness
    2. depression (CDHO Advisory); even subclinical hypothyroidism may affect mood
    3. bipolar symptoms
    4. may involve specific conditions, such as
      1. Alzheimer’s disease, especially in women
      2. autism.
  2. Myxedema, which  is associated with severe mental disorders including psychoses, and which may manifest as myxedema coma, which is 
    1. a medical emergency that occurs when the body’s level of thyroid hormones becomes extremely low
    2. treated with 
      1. intravenous thyroid hormone replacement and steroid medications
      2. supportive therapy (oxygen, breathing assistance, fluid replacement) and intensive-care nursing, as required
  3. Immune system disorders which may, in rare cases, be associated with
    1. chronic thyroiditis 
    2. other endocrine disorders such as
      1. adrenal insufficiency
      2. type 1 diabetes (CDHO Advisory). 
  4. Infections;  subacute thyroiditis 
    1. results in inflammation of the thyroid gland
    2. may be a complication of an upper respiratory infection
  5. Diabetes (CDHO Advisory)
  6. Heart disease 
  7. Obesity
  8. Goiter, goitrous hypothyroidism
  9. Infertility 

Oral health considerations

Resources consulted

The dental hygienist should be aware of the 

  1. oral and systemic manifestations of hypothyroidism so as to be able to 
    1. recognize the need for medical advice about
      1. the possibility of hypothyroidism in an undiagnosed patient, and the need to defer oral healthcare pending medical advice
      2. a diagnosed patient/client relative to
        1. the degree to which the hypothyroidism is controlled 
        2. complications
      3. a diagnosed patient/client who  has for some time been taking medications, and who is now experiencing symptoms of increased thyroid activity which may be but should not be attributed to the stress of oral healthcare, such as
        1. palpitations
        2. restlessness or shakiness
        3. sweating
        4. and, on questioning, acknowledges rapid weight loss
    2. take the medical history of a diagnosed patient relative to the
      1. hypothyroidism
      2. complications
      3. comorbidities
      4. current treatment
  2. oral health aspects of hypothyroidism
    1. children with hypothyroidism may have
      1. malocclusion
      2. delayed tooth eruption
      3. protruding tongue
      4. swollen gums
      5. increased risk of decay and periodontal disease
      6. poorly shaped teeth
    2. adults with hypothyroidism may have
      1. enlarged tongue
      2. delayed tooth eruption
      3. variable or poor periodontal health
      4. delayed wound healing
      5. changed taste sensitivity
      6. rapid and severe periodontal disease
      7. weakened oral and facial bones 
  3. the importance of cardiovascular issues associated with hypothyroidism, because medical advice may be required prior to the Procedures relative to
    1. atrial fibrillation, in regard to requirement for coagulation tests to assess hemostasis when anticoagulation medication is used by the patient
    2. caution regarding the use of epinephrine for patients who have cardiovascular disease
    3. potential for harm from stress in the course of oral healthcare for hypothyroid patients receiving treatment for heart disease that may increase energy consumption cardiac function, and therefore the load on the heart 
  4. the significance of lethargy and slowing of respiratory rate in diagnosed and medicated hypothyroidism patients may, during treatment, signal aspiration risk. 



Sourcing medications information

  1. Adverse effect database
  2. Specialized organizations
  3. Medications considerations
    All medications have potential side effects whether taken alone or in combination with other prescription medications, or as over-the-counter (OTC) or herbal medications.
  4. Information on herbals and supplements 

Treatment of Hypothyroidism

Resources consulted


  1. Treatment with thyroxine or its synthetic equivalent is continued for life and must not be stopped because the cause of the thyroid failure is likely to be progressive and permanent.
  2. The dose may have to be altered for major stress or illness, which can sometimes increase the need for thyroid hormone.
  3. For patients with heart disease, in older patients, or patients with co-existing or suspected heart disease, treatment is started with a low dose of thyroxine or synthetic equivalent to avoid aggravating conditions such as angina or other forms of heart disease.

Synthetic equivalent of thyroxine
levothyroxine (Synthroid®,  Eltroxin®, Levothroid®, Levoxyl®, Unithroid®)

Side effects of medications

See link above.


The dental hygienist in taking the medical and medications history-taking should 

  1. focus on screening the patient/client prior to treatment decision relative to
    1. medications considerations, including over-the-counter medications, herbals and supplements
    2. contraindications
    3. complications
    4. comorbidities
  2. explore the need for advice from the primary or specialized care provider(s)
  3. inquire about
    1. pointers in the history of significance to hypothyroidism, such as the oral health aspects of hypothyroidism in children
    2. symptoms indicative of problematic control of hypothyroidism, such as symptoms that could indicate that the medication dose is too high or too low
    3. the patient/client’s understanding and acceptance of the need for oral healthcare
    4. medications considerations, including over-the-counter medications, herbals and supplements
    5. problems with previous dental/dental hygiene care
    6. problems with infections generally and specifically associated with dental/dental hygiene care
    7. the patient/client’s current state of health
    8. how the patient/client’s current symptoms relate to
      1. oral health
      2. health generally
      3. recent changes in the patient/client’s condition. 


Identifying and contacting the most appropriate healthcare provider(s) from whom to obtain medical or other advice pertinent to a particular patient/client

The dental hygienist should

  1. record the name of the physician/primary care provider most closely associated with the patient/client’s healthcare, and the telephone number
  2. obtain from the patient/client or parent/guardian written, informed consent to contact the identified physician/primary healthcare provider
  3. use a consent/medical consultation form, and be prepared to securely send the form to the provider 
  4. include on the form a standardized statement of the Procedures proposed, with a request for advice on proceeding or not at the particular time, and any precautions to be observed.


Infection Control

Dental hygienists are required to keep their practices current with infection control policies and procedures, especially in relation to

  1. the CDHO’s Infection Prevention and Control Guidelines (2022)
  2. relevant occupational health and safety legislative requirements
  3. relevant public health legislative requirements
  4. best practices or other protocols specific to the medical condition of the patient/client.


  1. There may be contraindications to the Procedures, depending on the certainty of diagnosis and level of control. 
  2. With an otherwise healthy patient/client whose symptoms are under control and whose treatment is proceeding normally, the dental hygienist should implement the Procedures, though these may be postponed pending medical advice, which is likely to be required if the patient/client has
    1. Suspected undiagnosed hypothyroidism
    2. symptoms or signs of exacerbation of the medical condition
    3. comorbidity, complication or an associated condition of hypothyroidism
    4. not recently or ever sought and received medical advice relative to oral healthcare procedures
    5. recently changed significant medications, under medical advice or otherwise
    6. recently experienced changes in his/her medical condition such as medication or other side effects of treatment
    7. deep concerns about any aspect of his or her medical condition.


Dental hygienists are required to initiate emergency protocols as required by the College of Dental Hygienists of Ontario’s Standards of Practice, and as appropriate for the condition of the patient/client.

First-aid provisions and responses as required for current certification in first aid.


Subject to Ontario Regulation 9/08 Part III.1, Records, in particular S 12.1 (1) and (2), for a patient/client with a history of hypothyroidism, the dental hygienist should specifically record

  1. a summary of the medical and medications history
  2. any advice received from the physician/primary care provider relative to the patient/client’s condition
  3. the decision made by the dental hygienist, with reasons
  4. compliance with the precautions required
  5. all Procedure(s) used
  6. any advice given to the patient/client.


The dental hygienist should 

  1. urge the patient/client to alert any healthcare professional who proposes any intervention or test that he or she 
    1. has a history of hypothyroidism
    2. is taking medication for hypothyroidism
  2. should discuss, as appropriate 
    1. the importance of the patient/client’s
      1. self-checking the mouth regularly for new signs or symptoms
      2. reporting to the appropriate healthcare provider any changes in the mouth
    2. the need for regular oral health examinations and preventive oral healthcare 
    3. oral self-care including information about 
      1. choice of toothpaste
      2. tooth-brushing techniques and related devices
      3. dental flossing
      4. mouth rinses
      5. management of a dry mouth 
    4. the importance of an appropriate diet in the maintenance of oral health
    5. for persons at an advanced stage of the condition or who are debilitated
      1. regimens for oral hygiene as a component of supportive care and palliative care
      2. the role of the family caregiver, with emphasis on maintaining an infection-free environment through hand-washing and, if appropriate, wearing gloves
      3. scheduling and duration of appointments to minimize stress and fatigue 
    6. comfort level while reclining, and stress and anxiety related to the Procedures
    7. medication side effects such as dry mouth, and recommend treatment
    8. mouth ulcers and other conditions of the mouth relating to disorders of the adrenal gland, comorbidities, complications or associated conditions, medications or diet
    9. pain management. 



  1. Promotion of health through 
    1. oral hygiene for persons who have hypothyroidism
    2. early detection of inadequately controlled hypothyroidism
    3. recognition of complications that require medical advice prior to the Procedures.
  2. Recognizing the possibility of undiagnosed hypothyroidism, and referring the patient/client for medical advice.
  3. Reducing the risk that oral health needs are unmet.


  1. Causing risk to the patient/client by proceeding with oral healthcare without appropriate advice about a cardiovascular condition associated with the hypothyroidism.
  2. Performing the Procedures at an inappropriate time, such as 
    1. when the control of the patient/client’s hypothyroidism is problematic
    2. in the presence of complications for which prior medical advice is required
  3. Disturbing the normal dietary and medications routine of a person with hypothyroidism.
  4. Inappropriate management of pain or medication.






2011-02-01; 2016-11-07; 2021-07-06


College of Dental Hygienists of Ontario, regulatory body
Greyhead Associates, medical information service specialists


College of Dental Hygienists of Ontario


College of Dental Hygienists of Ontario, Practice Advisors


Dr Gordon Atherley
O StJ , MB ChB, DIH, MD, MFCM (Royal College of Physicians, UK), FFOM (Royal College of Physicians, UK), FACOM (American College of Occupational Medicine), LLD (hc), FRSA

Dr Kevin Glasgow

Lisa Taylor

Roula Anastasopoulos

Carolle Lepage


The College of Dental Hygienists of Ontario gratefully acknowledges the Template of Guideline Attributes, on which this advisory is modelled, of The National Guideline Clearinghouse™ (NGC), sponsored by the Agency for Healthcare Research and Quality (AHRQ), U.S. Department of Health and Human Services.

Denise Lalande
Final layout and proofreading

© 2009, 2011, 2016, 2021 College of Dental Hygienists of Ontario


1 Persons includes young persons and children