A Practical Approach to Special Care in Dentistry. Группа авторов

considering urgent dental treatment in a patient with untreated/significant hypothyroidismCognitive impairment is a common characteristic of congenital hypothyroidismSome patients can experience vision loss and/or hearing lossBradypsychia‐bradylalia has been reported in severe and long‐term hypothyroidismConsent/capacityPatients should be warned of the potential local (e.g. bleeding) and systemic complications (e.g. myxoedema coma), which can be triggered by dental treatmentConsider the impact of hypothyroidism on cognition and memoryAnaesthesia/sedationLocal anaesthesiaConsider risk of increased bleeding at the site of administrationSedationAvoid benzodiazepines such as diazepam and midazolam as they can trigger myxoedema comaGeneral anaesthesiaProcedures under general anaesthesia should be delayed until hormone levels have recoveredDental treatmentBeforeEnsure that the patient is compliant with their medical managementDetermine if there are any additional risks associated with the related comorbidities (e.g. anticoagulants due to arrhythmias)DuringCareful manipulation of soft tissues due to the bleeding and delayed healing riskAfterReduced bone turnover rate can increase the risk of radicular resorption secondary to orthodontic proceduresDrug prescriptionIncreased sensitivity to central nervous system depressants and barbiturates; avoid benzodiazepines and opioid analgesicsAvoid mouthwashes with povidone‐iodine (can increase the risk of thyroiditis or hypothyroidism)Education/preventionDue to their susceptibility to caries and periodontal disease, maintaining optimal oral hygiene and periodic professional dental reviews are a priority for these patients

Section II: Background Information and Guidelines

      Definition

      Hypothyroidism is a common pathological condition characterised by the thyroid gland's inability to produce sufficient thyroid hormone to satisfy the body's metabolic demands. Primary clinical hypothyroidism is defined as the coexistence of thyroid‐stimulating hormone (TSH) concentrations above the upper limit of normal and free thyroxine (T₄) concentrations below the reference range. In subclinical hypothyroidism (an early sign of thyroid gland failure), the TSH concentration is also above normal values, while T₄ concentrations are within the reference range. The mean prevalence in countries with adequate iodine intake is estimated at 1–2%. The disease is more common among women, in those older than 65 years and in white individuals.

      Aetiopathogenesis

       Primary hypothyroidism (due to thyroid hormone deficiency)May be related to iodine deficiency as iodine is a trace element essential for the synthesis of thyroid hormones, tri‐iodothyronine (T3) and thyroxine (T4)Iodine (as iodide) is found in the oceans; hence geographical areas that are iodine deficient tend to be inland and mountainous; more cases of congenital hypothyroidism (cretinism) are detected hereAutoimmune hypothyroidism (Hashimoto disease) is the most common cause in areas where there is sufficient iodine intakeDrugs can interfere with thyroid hormone production (e.g. amiodarone, lithium, some antiepileptic drugs, interferon‐alpha, some tyrosine kinase inhibitors)Iatrogenic causes include the administration of radioactive iodine to patients with hyperthyroidism, and those undergoing thyroid surgery or radiation therapy in the neckInfiltrative diseases which involve the thyroid gland may also be responsible (e.g. neoplasia)

       Secondary hypothyroidismCentral hypothyroidism: due to thyrotropin‐releasing hormone (TRH) deficiency or TSH deficiency and is associated with lesions in the hypothalamus and pituitary gland (mainly hypophysis adenoma), Sheehan syndrome, TRH resistance, radiation therapy to the brain and secondary to drugs such as dopamine, prednisone or opioidsFigure 5.2.3 Goitre (enlarged thyroid gland).Peripheral hypothyroidism: very uncommon and corresponds to an overexpression of deiodinase 3 (an enzyme that inactivates tyrosine) in patients with cancer and those with rare genetic syndromes

      Clinical Presentation

       Varies significantly (Table 5.2.2). Enlargement of the thyroid gland (goitre) can occur due to overstimulation in response to low thyroid levels (Figure 5.2.3)

       Determined by age, sex and progression time

       Ranges from asymptomatic forms to myxoedema crisis/coma (encephalopathy, hypothermia, seizures, hyponatraemia, hypoglycaemia, arrhythmias, cardiogenic shock, respiratory failure and fluid retention)

       Cretinism, classically the result of maternal iodine deficiency, is associated with growth retardation, developmental delay, mental retardation and thickened facial features

      Diagnosis

       Blood TSH concentration

       If the TSH concentration is high, the test should be repeated and T4 should be quantified

       The measurement of thyroid peroxidase antibodies can be useful for confirming the diagnosis of primary autoimmune hypothyroidism

       In the presence of additional clinical findings such as an irregular thyroid gland when palpated, ultrasonography is indicated (Figure 5.2.4)Table 5.2.2 Clinical manifestations of hypothyroidism.CategorySymptomsSignsGeneralFatigue Weight gain Intolerance to cold DrowsinessHypothermia Increased body mass index Reduced metabolic activity MyxoedemaCardiovascularShortness of breath Fatigue with exerciseHypertension Bradycardia Ischaemic heart disease Pleural effusionHaematologicalProne to bleedingAnaemia Von Willebrand diseaseMusculoskeletalJoint pain MyalgiaIncreased creatine phosphokinase levelsGastrointestinalIntake problems ConstipationOesophageal motility disorderSkin and hairDry skin Hair lossFine hair Thickened skin Loss of eyebrow tailSensorineuralHusky voice Dysgeusia Vision loss Hearing lossNeuropathy Cochlear dysfunctionEndocrinologicalInfertility Menstrual disorders GalactorrhoeaGoitre Blood sugar dysregulation Increase in prolactinPsychologicalMemory loss Depression DementiaCognitive impairment

Figure 5.2.4 Grey‐scale ultrasound and colour Doppler sonogram showing multiple micronodules in diffuse Hashimoto thyroiditis (right thyroid lobe).

      Management

       The treatment of choice is levothyroxine (a synthetic form of T4), at a dose of 1.5–1.8 μg/kg of body weight daily

       This is reduced in elderly patients or those with atrial fibrillation

      Prognosis

       The prognosis of hypothyroidism is dependent on its cause, and whether it is diagnosed and treated in a timely manner

       In the absence of treatment, hypothyroidism may have a risk of high morbidity and mortality, leading eventually to coma or even death

       Congenital hypothyroidism has potentially devastating neurological consequences, with failure to treat resulting in severe intellectual disability

       A leading cause of death in adults is cardiovascular diseases, predominantly heart failure

       Myxoedema coma is uncommon but is a medical emergency with a high mortality rate

       With treatment, most patients have a good prognosis, and the symptoms usually reverse in a few weeks or months

      A