Manejo Dental

VOLUME 39 NUMBER 2 FEBRUARY 2008 139

QUINTESSENCE INTERNATIONAL

Thyroid activity is controlled by the hypothal-

amic-pituitary-thyroid axis. Thyroid-releasing

hormone (TRH), secreted by the hypothala-

mus, induces the secretion of thyroid stimu-

lating hormone (TSH) by the anterior pitu-

itary, which in turn stimulates thyroid hor-

mone synthesis and secretion by the thyroid

gland.13 The thyroid gland is a bilobular

structure that lies on either side of the tra-

chea.1 Its functional unit is the thyroid follicle

made up of thyroid follicular cells (TFCs).4

TFCs selectively remove iodine from the

blood and synthesize iodothyronines (thyrox-

ine [T4], triiodothyroxine [T3], and reverse

triiodothyronine [rT3]).1 The enzyme respon-

sible for the synthesis of iodothyronines is

thyroid peroxidase (TPO). The approximate

proportions of T4, T3, and rT3 produced are

90%, 10%, and less than 1%, respectively. rT3appears to have no biologic function.5 Once

secreted into the bloodstream, approximately

70% of T4 and T3 binds to thyroxine-binding

globulin (TBG), while the remaining 30%

binds to transthyretin, albumin, and lipopro-

teins.1 A small percentage of T3 and T4(< 0.2%) circulates in an unbound, free state

and acts to maintain physiological hormone

levels by negative feedback mechanisms

involving the hypothalamus, pituitary, and

thyroid glands.6

Risk stratification and dental management of the patient with thyroid dysfunctionMichaell A. Huber, DDS1/Gza T. Terzhalmy, DDS, MA2

The thyroid gland produces hormones critical to the maintenance of the cellular metabolic

rate. The actions of these hormones are far-reaching, affecting thermoregulation and

calorigenesis; the metabolism of carbohydrates, fats, and proteins; and oxygen utilization.

Thyroid hormones also appear to act synergistically with epinephrine and enhance tissue

sensitivity to catecholamines. Signs and symptoms of hypothyroidism include listlessness,

fatigue, cold intolerance, dry skin, hair loss, constipation, weight gain, muscle soreness,

and slow heart rate. Signs and symptoms of hyperthyroidism include irritability, heat intol-

erance, tremors, increased sweating, frequent bowel movements, and quickened heart

rate. The effect of inadequately treated or undiagnosed hyperthyroidism on the heart car-

ries perioperative risks. To provide competent dental care to patients with thyroid dysfunc-

tion, clinicians must understand the disease, its treatment, and the impact the disease and

its treatment may have on the patients ability to undergo and respond to dental care.

(Quintessence Int 2008;39:139150)

Key words: dental care, hyperthyroid, hypothyroid, thyroid dysfunction

1Associate Professor and Head, Division of Oral Medicine,

Department of Dental Diagnostic Science, The University of

Texas Health Science Center at San Antonio, Dental School, San

Antonio, Texas.

2Endowed Professor in Clinical Dentistry, Dental School, and

Professor, Department of Pharmacology, Graduate School of

Biomedical Sciences, The University of Texas Health Science

Center at San Antonio, San Antonio, Texas.

Correspondence: Dr Michaell A. Huber, Division of Oral

Medicine, Department of Dental Diagnostic Science, The

University of Texas Health Science Center at San Antonio, Dental

School, Mail Code 7919, 7703 Floyd Curl Drive, San Antonio,

Texas, 78229-3900. Fax: 210-567-6348. E-mail: huberm@

uthscsa.edu

Huber1.qxd 12/18/07 2:35 PM Page 139

COPYRIGHT 2008 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER

140 VOLUME 39 NUMBER 2 FEBRUARY 2008

QUINTESSENCE INTERNATIONALHuber/Terzhalmy

ETIOLOGY AND EPIDEMIOLOGY

T4 serves as a prohormone for the extrathy-

roidal production of T3, which, in its free form,

accounts for most of the biological activity of

thyroid hormones.6 T3 stimulates RNA poly-

merase and phosphoprotein kinases and the

synthesis of nuclear proteins, which are

involved in the regulation of growth and

development; thermoregulation and calorige-

nesis; the metabolism of carbohydrates, pro-

teins, and lipids; and oxygen consumption.1

Thyroid hormones also appear to act syner-

gistically with epinephrine to enhance

glycogenolysis and hyperglycemia and

enhance tissue sensitivity to catecholamines.

Yet, there appears to be a paradoxical

inverse relationship between circulating nor-

epinephrine and thyroid hormone levels.710

While the myocardial effects of excess thy-

roid hormone mimic a hyperadrenergic state,

the levels of circulating catecholamines, in

these scenarios, are actually low or normal. It

is postulated that the increased sympath-

omimetic response may be due to thyroid

hormone-induced increase in myocardial

sensitivity, increased responsiveness to !-

adrenergic receptor activation or possibly an

up-regulation of adrenergic receptors.7 The

reduced peripheral resistance observed in

thyroid excess may be associated with a

reduced contractile response to norepineph-

rine (possibly through !1-adrenergic and/or

!2-adrenergic receptor modulation) and

enhanced acetylcholine-induced vasodilata-

tion.11 However, others postulate that

increased endothelial production of nitric

oxide (NO), observed in thyroid excess,

underlies the reduced peripheral resistance

observed.9

Patients with thyroid dysfunction may be

characterized as euthyroid, hypothyroid, or

hyperthyroid to reflect normal, inadequate, or

excessive hormonal secretion, respectively

(Table 1).12 Some thyroid disorders manifest

polar clinical progressions, whereby initial

glandular hypersecretion evolves into a state of

hyposecretion. Many of the more common thy-

roid disorders (Graves disease, Hashimotos

thyroiditis, postpartum thyroid dysfunction,

and painless sporadic thyroiditis) represent

autoimmune phenomenas.13,14 In addition to

genetic predisposition, numerous environ-

mental factors, such as low birth weight, iodine

deficiency or excess, selenium deficiency, the

use of oral contraceptives and other medica-

tions, stress, allergy, smoking, ionizing radia-

tion, and bacterial or viral infection, have been

postulated to contribute to etiopathogenesis of

autoimmune thyroid disease.14

Disorders characterized by euthyroidismEuthyroid goiter (diffuse, nodular, multinodular)Benign tumorsMalignant tumors

Differentiated (papillary, follicular)Undifferentiated (small cell, giant cell)Medullary

ThyroiditisAcuteSubacute thyroiditis (de Quervains)Chronic autoimmune (Hashimotos disease)PostpartumReidels thyroiditis

Disorders characterized by hypothyroidismWith hypothyroidism

Primary hypothyroidismChronic autoimmune thyroiditis Iatrogenic (surgery, 131I [radioiodine] therapy)Diffuse and nodular goiterSevere iodine deficiency

Neonatal congenital hypothyroidismSecondary hypothyroidism

Pituitary hypothyroidismTertiary hypothyroidism

Hypothalamic hypothyroidismWithout hypothyroidism

Generalized and peripheral resistance to thyroidhormones

Transient hypothyroidism (iodinedeficiency/excess, druginduced, postpartum)

Disorders characterized by hyperthyroidismGlandular hyperfunction

Diffuse hyperthyroid goiter with thyroid associatedophthalmopathy (Graves disease)

Multinodular hyperthyroid goiter or Plummersdisease

Autonomous noduleThyrotoxicosis (without thyroid gland hyperfunction)

Excessive exogenous thyroid hormonesPost-inflammatory or from glandular destructionAmiodarone induced

Transient hyperthyroidism

Table 1 Common thyroid disorders12

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The actual prevalence of thyroid disorders

is unknown. The Thyroid Foundation of

America estimates that 10 million Americans

suffer from a hypothyroid disorder and 4.5

million Americans suffer from a hyperthyroid

disorder, of whom 8 million and 600,000,

respectively, are undiagnosed.15 As is the

case with most autoimmune diseases, there

is a clear female preponderance, with a

female-to-male ratio of about 5 to 10:1.14 An

estimated 5% of individuals in the United

States have palpable thyroid nodules, of

which 95% are benign (roughly 85% hyper-

plastic nodules, 15% adenomas, and less

than 1% cysts).16 In 2006, an estimated

30,180 cases of thyroid carcinoma were diag-

nosed in the United States (7,590 men and

22,590 women).17 Thyroid carcinoma is most

frequently papillary (81%), followed by follicu-

lar and Hrthle-cell (14%), medullary (3%),

and anaplastic (2%) forms.16

CLINICAL MANIFESTATIONS

It must be emphasized that, in many cases,

the natural history of a thyroid disorder may

be marked by subtle periods of remission

and exacerbations.12 Conversely, either

extreme hypothyroidism or extreme hyper-

thyroidism may evolve into a life-threatening

medical emergency.

HypothyroidismHypothyroidism is a clinical disease state

occurring when there is insufficient thyroid

hormone available to target tissues (Table 1).

Classification (cretinism versus myxedema)

by age of onset is important because the

clinical presentations will vary substantially.

CretinismCongenital hypothyroidism occurs at an over-

all incidence of approximately 1:3,000 to

4,000 births, with a slightly higher prevalence

in the Hispanic population and a decreased

prevalence in African-Americans.18 About

85% of the cases are likely due to sporadic

thyroid dysgenesis (agenesis), while the

other 15% are due to an autosomal recessive

mode of inheritance.19 Congenital hypothy-

roidism (cretinism) is a recognized cause of

mental retardation. The clinical manifesta-

tions of hypothyroidism are difficult to recog-

nize at birth, and it isnt usually until the third

month of life that symptoms begin to appear.

By this time, substantial neurological and

mental retardation may have occurred.

MyxedemaMyxedema usually develops gradually over a

period of months or years (Fig 1). Signs and

symptoms include coarse facial features

(such as thick lips, puffy eyelids, and a sad

expression), dry hair, slow speech, lethargy,

memory impairment (depression), cardiovas-

cular abnormalities (including slow pulse

rate, hypotension, cardiomegaly, low-ampli-

tude QRS, and inverted T waves), increased

sensitivity to cold, decreased sweating, dry

and cold skin, muscle weakness, and

reduced respiratory rate. A characteristic

nonpitting tissue edema is frequently ob-

Fig 1 Myxedema is characterized by coarse facialfeatures,accented by thick lips,macroglossia,puffy eye-lids, dry hair and skin, and a lethargic sad expression.

Huber1.qxd 12/18/07 2:35 PM Page 141



served.8,20 It is postulated to be a conse-

quence of the deposition of mucopolysac-

charides and a viscid proteinaceous fluid

within tissues.21,22 The tongue and laryngeal

tissues are often affected, resulting in slurred

speech, hoarseness, and impaired sleep pat-

terns.21,23 A rather characteristic loss of the

outer third of the eyebrow is frequently

observed.20,21,24 Laboratory abnormalities

may include evidence of anemia and elevat-

ed levels of aspartate transaminase, alanine

transaminase, lactate dehydrogenase, creati-

nine, and cholesterol.5

Myxedema coma is an extreme life-threat-

ening complication of hypothyroidism.

Typically, the patient is elderly and has a his-

tory of hypothyroidism.3,25 Most cases are

preceded by precipitating factors such as

infection, exposure to cold, sedative drug

therapy, lung disease, stroke, congestive

heart failure, gastrointestinal bleeding, acute

trauma, or noncompliance with thyroid sup-

plementation.26 The patient manifests wors-

ening alveolar hypoventilation, hypothermia,

bradycardia and decreased cardiac contrac-

tility, hyponatremia and decreased glomeru-

lar filtration, and rarely coma.27 Management

requires prompt administration of thyroid

hormone and supportive measures (ie, venti-

latory support, fluid restoration, glucose

administration, and glucocorticoid adminis-

tration) to stabilize and reverse the down-

ward spiral. Mortality rates of 20% to 60%

have been reported. 27

HyperthyroidismHyperthyroidism is a clinical disease state

produced by the effects of excessive thyroid

hormone on peripheral tissues (Table 1). The

severity of the illness caused by thyrotoxico-

sis is related to the severity and duration of

the hormone excess, the age of the patient,

and the presence or absence of other disease.

Hyperthyroidism occurs most frequently in

women of childbearing age and may mani-

fest as a goiter, tremor, excitability, emotional

instability, rapid pulse rate (tachycardia, atrial

fibrillation), heart murmur, hypertension,

rapid respiration, facial flushing, warm and

moist skin, increased appetite with weight

loss, muscle wasting, enlarged palpable

lymph nodes, and exophthalmos often asso-

ciated with symptoms of a gritty sensation,

light sensitivity, increased tearing, double

vision, and a feeling of retroocular pressure

(Figs 2 and 3).28 Laboratory abnormalities

may include hypercalcemia and elevated lev-

els of alkaline phosphatase, aspartate

transaminase, and alanine transaminase.5

Osteoporosis typically affects cortical (hip

and forearm) rather than trabecular bone

(spine). 29


Figs 2 and 3 Common signs and symptoms ofhyperthyroidism include a goiter and exophthalmosoften associated with symptoms of a gritty sensa-tion, light sensitivity, increased tearing, doublevision, and a feeling of retroocular pressure.

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Thyroid storm is the extreme manifesta-

tion of hyperthyroidism. Its uncommon and

occurs most frequently in patients with

Graves disease, toxic adenomas, toxic

multinodular goiters, and hypersecretory thy-

roid carcinoma.26 Predisposing factors

include infection, nonthyroid trauma, psy-

chosis, parturition, myocardial infarction,

intake of radioiodine and high doses of

iodine-containing compounds, thyroid trau-

ma, the discontinuation of antithyroid drug

therapy, and the recent institution of amio-

darone therapy.25 Cardinal clinical findings

include fever (greater than 101.3F), tachy-

cardia, CNS dysfunction (including agitation,

confusion, and delirium), and gastrointestinal

dysfunction (such as nausea, vomiting, and

diarrhea).25,26 Other potential findings include

diaphoresis, atrial fibrillation, and congestive

heart failure.3,26 Management in an intensive

care unit includes the administration of !-

adrenergic blocking agents, propylthiouracil,

and supportive measures (such as external

cooling and careful fluid resuscitation). 25

DIAGNOSIS

Patients with a suspected thyroid disorder

should undergo a thorough physical evalua-

tion, including an exhaustive medical history,

physical examination, and appropriate labo-

ratory testing. A thyroid disorder may develop

insidiously over time, and the suspect signs

and symptoms are easy to overlook. This

fact, combined with the dynamic nature of

some thyroid disorders and the limited sensi-

tivity/specificity of available tests, can chal-

lenge the diagnostic acumen of even the

most experienced clinician.

CretinismMandatory screening of TSH levels in new-

borns allows for the early identification of con-

genital hypothyroidism and the prompt institu-

tion of management strategies aimed at reduc-

ing neurological impairment (cretinism).30,31

Adult Hypo- or HyperthyroidismSerum TSH concentrations represent the

most reliable indicator of thyroid status.26 The

American Thyroid Association recommends

that all patients obtain a serum TSH determi-

nation at age 35 and every 5 years there-

after.32 In general, results demonstrating a

high TSH and low free T4 (FT4) are indicative

of hypothyroidism, while results demonstrat-

ing a low TSH and a high FT4 are indicative

of hyperthyroidism.6 Following initial TSH

measurements, specialized testing may be

performed.33 For nodular disease, this may

include a needle-aspiration biopsy to rule out

malignancy.34,35 For cases of suspected

autoimmune thyroid disease, antithyroid anti-

body testing (antithyroglobulin antibody

[TgAb], anti-TPO antibody [TPOAb], antithy-

roid receptor antibody [TRAb], and thyroid

stimulating antibody) may prove valuable.6

Scintigraphy may be useful in determining

nodular functional status in hyperthyroidism

(Graves disease or multinodular goiter), fol-

licular neoplasm, and multinodular goiter.36,37

PRINCIPLES OF MEDICALMANAGEMENT

HypothyroidismWith early detection and medical manage-

ment, permanent mental retardation may be

avoided in the young. Purified or synthetic

thyroid preparations are available for replace-

ment therapy. Thyroxine, in the form of

levothyroxine, is the most widely prescribed

treatment for hypothyroidism in the United

States (Table 2).38 The amount of thyroid hor-

mone given to restore the euthyroid state

varies, but for adults, it usually lies between

0.05 to 0.15 mg (50 to 150 micrograms) of

levothyroxine or its equivalent daily. Patients

usually notice an improvement two to three

weeks after the start of treatment. Reductions

in weight and puffiness and increases in the

pulse rate and pulse pressure occur early in

treatment, but other signs and symptoms

may take months to resolve. The need for thy-

roid hormone may decrease slightly with age

and increase somewhat with stress and

infection. Inadequate thyroxine-replacement

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therapy is associated with continued clinical

features of hypothyroidism. Substantial over-

treatment with thyroxine results in clinical

manifestations of hyperthyroidism.

Hyperthyroidism Antithyroid drugs are the cornerstones in the

management of hyperthyroidism (Table 3). 39,40

They may be used as primary treatment for

hyperthyroidism or preparative therapy before

surgery or radioiodine therapy. Antithyroid

drugs are usually discontinued or tapered

after 12 to 18 months of therapy. Lifelong fol-

low-up is required for patients in remission,

since spontaneous hypothyroidism may devel-

op decades later. Iodine or iodide prepara-

tions may be prescribed as adjunctive therapy

for short-term benefits and to decrease the

size and vascularity of the thyroid gland in

preparation for surgery. Radioactive iodine,

given orally in the treatment of older patients

with thyrotoxicosis, accumulates in the storage

follicles and emits beta rays with a half-life of 5

days, which destroys a portion of the hyperac-

tive gland. Beta-adrenergic antagonists may

be used to suppress some of the symptoms of

hyperthyroidism, such as tremor, anxiety, and

tachycardia.

ORAL MANIFESTATIONSOF THYROID DYSFUNCTION

With few exceptions, the oral manifestations

attributable to thyroid dysfunction are neither

well-established nor consistent and are large-

ly based on anecdotal case reports. The age

of onset, severity, and duration of any thyroid

dysfunction directly affects the likelihood of

any potential oral manifestations. Thus, the

presence of associated oral manifestations is

more likely to occur at either end of the thy-

roid dysfunction spectrum (ie, extreme

hypothyroidism or extreme hyperthyroidism).

HypothyroidismCretinism. The oral complications of undiag-nosed and untreated congenital thyroid hypo-

function include the characteristic facies of

cretinism (puffy face, disproportionately large

Adverse drug Drug Mechanisms of action Indication effects (ADEs)

Levothyroxin T4 and T3 replacement (T4 is Drug of choice No ADEs at therapeuticconverted to T3 in plasma) dosages

Hyperthyroidism at overdose

Liothyronine T3 replacement Used when levothyroxin is notabsorbed adequately

Liotrix T4 and T3 replacement Used when the conversion of levothyroxin from T4 to T3 is abnormal

Table 2 Drugs used to treat hypothyroidism

Adverse drug Drug Mechanisms of action Indication effects (ADEs)

Methimazole Inhibits the transformation of Long-term thyroxin suppression Agranulocytosis, hepatotoxicity,inorganic iodine to organic or in preparation for surgery urticarial or macular reactions,iodine or 131I therapy arthralgia, sialadenitis (rarely)

with methimazolePropylthiouracil Inhibits the transformation

of inorganic iodine to organic iodine and blocks the conversion of T4 to T3

Iodine or iodide Short term inhibition of Adjunctive therapy to the drugsthyroxin release above and in preparation for

surgery

Table 3 Drugs used to treat hyperthyroidism

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cranium, dull expression, flat and broad nose,

macroglossia, malocclusion, thick everted

lips, and an open mouth). 41 There are con-

flicting reports of altered tooth morphology

(hypoplastic versus unaltered) and eruptive

patterns (delayed versus normal). 4144

Myxedema. The principal oral findingassociated with chronic hypothyroidism in

adults is macroglossia (Fig 1).21,4446 The

nose, eyelids, and lips may be edematous.

Caries risk has been variably reported as

increased, normal, or decreased.41 Impaired

periodontal health has been reported, but it

is unclear whether this finding is related to a

lack of adequate patient compliance with

hygiene procedures, altered bone metabo-

lism, or both.41,47 Some patients may experi-

ence dysgeusia. Salivary gland enlargement,

especially of the parotid and sublingual

glands, has been reported.48

HyperthyroidismChildren with hyperthyroidism may experi-

ence early loss of deciduous teeth and early

eruption of the permanent dentition.5,42 Other

potential findings in either the child or adult

hyperthyroid patient include tremor of the

lips and tongue, increased caries risk, accel-

erated alveolar ridge atrophy, and increased

incidence of mucosal erosions (burning

mouth syndrome).5,42 The characteristic

exophthalmos often observed in Graves dis-

ease might be striking. Lid retraction with

exposure of the white sclera above the lim-

bus produces a characteristic stare.24 Other

findings include lid lag, proptosis, diplopia,

and decreased visual acuity.

PRINCIPLES OF DENTALMANAGEMENT

GoalsWhen treating patients with thyroid dysfunc-

tion in the oral healthcare setting, the goals

are to develop and implement timely preven-

tive and therapeutic strategies compatible

with the patients physical and emotional

ability to undergo and respond to dental

care, as well as the patients social and psy-

chological needs and desires.

Patient assessmentThe first priority for the dental practitioner is

to obtain a meticulous medical history and

perform a thorough head and neck examina-

tion. The presence of signs and symptoms of

a potential thyroid dysfunction mandate a

medical consultation for further evaluation.5,24

Medical historyFor patients with an acknowledged thyroid

dysfunction, it is essential to assess the

patients current status and identify potential

comorbidities, which may necessitate a mod-

ification to the delivery of dental care.

Identifiable risk factors for thyroid dysfunc-

tion from the medical history include previ-

ous thyroid dysfunction; goiter; surgery or

radiotherapy of the thyroid gland; diabetes

mellitus (DM); vitiligo; pernicious anemia;

leukotrichia; medications such as lithium car-

bonate and iodine-containing drugs; and a

family history of diabetes mellitus, pernicious

anemia, thyroid disease, or primary adrenal

insufficiency.32 Clinicians should also seek to

determine the presence or absence of car-

diovascular diseases (such as angina pec-

toris, coronary artery disease, arrhythmias,

and congestive heart failure). There is some

evidence that patients with hyperlipidemia

associated with overt hypothyroidism have

an increased incidence of coronary artery

disease and associated angina pectoris.38,49

Furthermore, some patients with hypothy-

roidism cannot tolerate full replacement

therapy because of angina pectoris and

increased incidence of myocardial infarction

and sudden death.38 There is also evidence

that patients treated for thyroid disease

(Graves disease, toxic multinodular goiter,

Hashimotos thyroiditis) have an increased

long-term cardiovascular risk despite restora-

tion of euthyroidism.50

Functional capacity. Since T4 and T3exert direct inotropic and chronotropic

effects on cardiac muscle and appear to act

synergistically with epinephrine, the history

should also seek to determine the patients

functional capacity. Functional capacity,

which is expressed in terms of metabolic

equivalents (METs), is a measure of an indi-

viduals ability to perform a spectrum of com-

mon daily tasks (physical stressors). Cardiac

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risk in association with noncardiac proce-

dures is increased in patients unable to meet

a 4-MET demand during normal daily activi-

ties. 5153 Four METs is approximately equiva-

lent to the physiological stress produced by

doing light yard work (such as raking leaves,

weeding, or pushing a power mower), paint-

ing, doing light carpentry, or climbing a flight

of stairs. The hemodynamic effects of 4

METs is equivalent to that produced by 0.045

mg of epinephrine.54

Physical examinationGeneral appearance. The hypothyroidpatient may present with coarse facial fea-

tures (thick lips, puffy eyelids, sad expression),

dry hair, and dry and cold skin. The hyperthy-

roid patient may manifest tremor, excitability,

warm and moist skin, and exophthalmos.

Vital signs. Thyroid hormones appear toact synergistically with epinephrine affecting

cardiac contractility, vascular tone, and blood

pressure. As a result of this increased sym-

pathomimetic activity, heart rate, blood pres-

sure, and the rate of respiration are increased

in the hyperthyroid and decreased in the

hypothyroid patient. Myxedema coma is an

extreme life-threatening complication of

hypothyroidism. It is characterized by

hypoventilation, hypotension, and bradycar-

dia. A blood pressure of < 90/50 mm Hg is a

reliable sign of shock. Thyroid storm is the

extreme manifestation of hyperthyroidism. It

is characterized by an elevated temperature,

tachycardia, and high blood pressure. A

blood pressure in excess of 180/110 mm Hg

represents a hypertensive crisis. A resting

pulse rate below 60 or above 100 beats per

minute in adults, if symptomatic (sweating,

weakness, dyspnea, and/or chest pain),

should be considered a cardiac risk in

association with noncardiac procedures.

Respiratory rates less than 10 or greater that

20 breaths per minute may indicate respira-

tory distress.

Head and neck examination. Everypatient should be clinically screened for a

thyroid abnormality as part of the routine

head and neck examination.5,37,42 Normal thy-

roid tissue is often difficult to distinguish in

the relaxed neck; however, having the patient

extend the neck to one side allows for easier

palpation of the thyroid lobule on the opposite

side. The thyroid gland should be assessed

for textural consistency, overall size, presence

of growths, and tenderness. 5,37 The presence

of multinodularity of similar consistency is

most consistent with a benign goiter, while

the presence of a midline mass that moves

up with protrusion of the tongue is likely to be

a thyroglossal duct cyst.37

Treatment strategiesAs noted earlier, both hypothyroidism and

hyperthyroidism adversely affect cardiac

function. Thyroid dysfunction may also be

associated with DM and adrenal disease

(autoimmune polyglandular syndrome, type 2).

Consequently, treatment strategies for a

patient with thyroid dysfunction (Table 4)

should take into consideration the patients

overall health as reflected by the patients

medical history and vital signs. The dental

management of patients with cardiovascular

diseases, DM, and adrenal dysfunction

has been extensively reviewed in recent

publications. 5560

The hypothyroid patientThere are no randomized, prospective studies

in dentistry or medicine looking at surgical

outcomes in hypothyroid patients versus

controls. However, two retrospective case-

matched controls can provide some guid-

ance with relevance to dentistry. In one study,

researchers reviewed anesthetic and surgical

outcomes in 59 hypothyroid patients and 59

paired euthyroid controls.61 There were no dif-

ferences between the groups in perioperative

complications, surgical outcome, or length of

hospital stay. There were also no differences

in outcome among subsets of hypothyroid

patients as determined by thyroxine levels;

however, only a few patients were severely

hypothyroid. The authors concluded that

there was no evidence to justify deferring nec-

essary surgery in patients with mild to moder-

ate hypothyroidism and not enough evidence

to make recommendations for patients with

severe hypothyroidism. A severe hypothyroid

patient is one with myxedema characterized

by delayed mentation, pericardial effusions,

heart failure, or very low levels of thyroxine.62

In the second study, investigators looked

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at perioperative complications in 40 hypothy-

roid patients compared with 80 matched con-

trols. 63 Hypothyroid patients had more intra-

operative hypotension in noncardiac surgery,

but there were no differences between the

groups in perioperative arrhythmias or dura-

tion of hospitalization.

The use of local anesthetic agents andanalgesics. A review of the literature revealedno adverse effects associated with epineph-

rine infusion in patients with hypothyroidism

without significant cardiovascular disease.58

Well-controlled, medically supervised patients

on thyroid replacement and patients with mild

to moderate symptoms of hypothyroidism

may safely undergo routine dental care under

local anesthesia. However, patients with

hypothyroidism are hyperreactive to central

nervous system depressants (opioid anal-

gesics, anxiolytic agents), which should there-

fore be administered judiciously.5

The hyperthyroid patientT4 and T3 exert direct inotropic and chrono-

tropic effects on cardiac muscle. Left ventricu-

lar ejection fraction may not increase normally

during physiological stress, and increased

cardiac output may limit cardiac reserves dur-

ing surgery in the hyperthyroid patient.65

Consequently, the effect of inadequately treat-

ed or undiagnosed hyperthyroidism on the

heart carries perioperative risks. If hyperthy-

roidism is suspected, because of either med-

ical history or clinical signs and symptoms, the

patient should be referred for evaluation by an

internist or endocrinologist. Once medical

treatment has been instituted and the patient

is euthyroid, there is no contraindication to

dental treatment.

The use of local anesthetic agents andanalgesics. The use of local anestheticagent containing a vasoconstrictor in

patients with high concentrations of T4 and

T3 is an area of concern.5,24,42,66 Thyroid hor-

mones appear to act synergistically with epi-

nephrine by increasing tissue sensitivity to

catecholamines and possibly up-regulating

adrenergic receptors. An additional problem

associated with the use of local anesthetic

agents containing epinephrine is related to

the treatment of hyperthyroid symptoms with

a nonselective !-adrenergic antagonist. 5,67

However, these concerns must be balanced

against the value of a vasoconstrictor in

Euthyroid patient OR patient with mild to moderate thyroid dysfunction AND/OR minor clinical predictors(advanced age, atrial fibrillation, history of stroke) OR intermediate clinical predictors (stable angina pectoris, pre-vious myocardial infarction [MI], compensated heart failure renal insufficiency) of cardiovascular risk

Blood pressure less than 180/110 mm Hg; normal pulse pressure, rate and rhythm; functional capacity greaterthan 4 METsComprehensive dental careRoutine referral for medical management and risk factor modification

Blood pressure less than 180/110 mm Hg; normal pulse pressure, rate and rhythm; BUT functional capacityless than 4 METs Appropriate limited dental care*Routine referral for medical management and risk factor modification

Blood pressure greater than 180/110 mm Hg OR systolic blood pressure less than 90 mm Hg AND/OR abnor-mal pulse pressure, rate, or rhythm Appropriate emergency dental care**If patient is symptomatic, immediate referral for medical management and risk factor modification If patient is asymptomatic, routine referral for medical management and risk factor modification

Patient with severe hypothyroidism OR thyrotoxicosis AND/OR major clinical predictors (unstable coronary syn-drome, decompensated heart failure, severe valvular disease, significant arrhythmias) of cardiovascular risk

Appropriate emergency dental care**Immediate referral for medical management and risk factor modification

* Limited office care may include dental prophylaxis, restorative procedures, simple periodontal and endodontic procedures, androutine extractions.** Emergency office care under local anesthesia without a vasoconstrictor should be based on firm evidence that the benefitsachieved by therapeutic intervention outweigh the risk of complications associated with the patient's diabetic or cardiovascularstatus and may include activities related to pain relief, the treatment of infection (including simple incision and drainage), and theinduction of hemostasis (avoid the use of epinephrine to control local bleeding).

Table 4 Dental management of the patient with thyroid dysfunction

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inducing profound local anesthesia, which is

essential in reducing the physiologic stress

associated with pain. For the patient with

overt evidence of hyperthyroidism, the use of

vasoconstrictors should be avoided. For all

other scenarios, the cautious use of vaso-

constrictors, based on the patients function-

al capacity, should be considered. For those

patients whose functional capacity is equal

to or greater than 4 METs, 4.5 mL of a local

anesthetic agent with epinephrine 1:100,000

(or equivalent) can be administered safely.

Furthermore, combination analgesics con-

taining acetylsalicylic acid (ASA) are con-

traindicated in patients with hyperthyroidism

because ASA interferes with the protein bind-

ing of T4 and T3, thereby increasing their free

form, and can lead to thyrotoxicosis.

Preventive strategiesSome patients with hyperthyroidism may be

treated with 131I (radioiodine) for the short-

term inhibition of thyroxin release. Salivary

glands are known to concentrate iodide

selectively (up to 24% of administered 131I is

lost through the saliva). To reduce the poten-

tial for 131I-induced sialadenitis, it is recom-

mend that measures be taken to increase

salivation and thus accelerate the flow of 131I

through the glandular parenchyma.59 These

patients may benefit from simple measures

such as eating carrots or celery or chewing

sugarless or xylitol-containing gums. How-

ever, pilocarpine hydrochloride (Salagen,

MGI Pharma) and cevimeline hydrochloride

(Evoxac, Daiichi Pharmaceuticals), both mus-

carinic agonists, may more predictably

increase salivary activity. The use of the

radioprotectant agent amifostine has also

been advocated. The patient who manifests

residual salivary gland damage should be

managed in a manner similar to that estab-

lished for the patient who has received thera-

peutic head and neck radiotherapy. 60

CONCLUSIONS

When treating patients with thyroid dysfunc-

tion in the oral healthcare setting, the goals

are to develop and implement timely preven-

tive and therapeutic strategies compatible

with the patients physical and emotional

ability to undergo and respond to dental

care. There is no evidence to justify deferring

necessary dental procedures in patients with

mild to moderate hypothyroidism. However,

T4 and T3 exert direct inotropic and

chronotropic effects on cardiac muscle. Left

ventricular ejection fraction may not increase

normally during physiological stress, and

increased cardiac output may limit cardiac

reserves during stressful procedures in the

hyperthyroid patient. The effect of inade-

quately treated or undiagnosed hyperthy-

roidism on the heart may carry perioperative

risks in the oral healthcare setting.

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