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THE THYROID THE THYROID GLAND GLAND HYPERTYROIDISM HYPERTYROIDISM
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THE THYROID GLAND

Jan 03, 2016

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Priscilla Hunt

THE THYROID GLAND. HYPERTYROIDISM. THE THYROID GLAND. The thyroid secretes primarily Thyroxine / T 4 / T 4 is probably not metabolically active until converted to T 3 (T 4 = prohormone) ~85% of T 3 is produced by monodeiodination of T 4. THE THYROID GLAND. - PowerPoint PPT Presentation
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  • THE THYROID GLANDHYPERTYROIDISM

  • THE THYROID GLANDThe thyroid secretes primarilyThyroxine / T4 /T4 is probably not metabolically active until converted to T3(T4 = prohormone)~85% of T3 is produced by monodeiodination of T4

  • T3 and T4 circulate in plasma are almost entirely (>99,9%) bound to transport proteins (mainly TBG, less TBPA and albumins)Only free hormones exert its metabolic actionIt is better to measure the concentration in plasma FT3 or FT4THE THYROID GLAND

  • Patterns of thyroid function test results in patients with hyperthyroidismConventional hyperthyroidism (95% of cases):FT4 ; FT3 ; TSH or undetectableT3-hyperthyroidism (5% of cases):FT4 ; FT3 ; TSH or undetectableSubclinical hyperthyroidism:FT4 ; FT3; TSH or undetectable

    NEGATIVE FEEDBACK

  • Not-thyroidal illness (e.g. myocardial infarction or pneumonia):Decreased peripherial conversion of T4 to T3.Alterations in the binding proteins.Alterations in the affinity of binding proteins for thyroid hormones.TSH levels as a results of the illness itself or the use of drugs (e.g. dopamine or corticosteroids).TSH into the hypothyroid range during convalescence.

  • THYROTOXICOSIS Hypermetabolic state caused by thyroid hormone excess at the tissue levelHYPERTHYROIDISMIncreased thyroid hormones synthesis and secretionAll patients with hyperthyroidism have thyreotoxicosis Not all patients with thyreotoxicosis are hyperthyroid

  • AETIOLOGYIt is important to identify the cause of hyperthyroidism in order to prescribe appropriate treatmentPREVALENCEFemales:~20/1000Males:~4/1000

  • Causes of thyrotoxicosiscommon typesWith high RAIUGraves diseases (60-90%)Multinodular goitre (14%)Autonomously functioning solitary thyroid nodule (5%)Iodine-induced thyrotoxicosisWith low RAIUThyroiditissubacute (3%)silent (painless)post-partumIodine-induced thyrotoxicosisdrugs (e.g. amiodarone)radiografic contrast mediaiodine prophylaxis programme

  • Causes of thyrotoxicosisuncommon typesWith high RAIUCongenital hyperthyroidismTSH-induced hyperthyroidismTSH-secreting adenomaselective pituitary resistance to thyroid hormoneTrophoblastic tumors

    With low RAIUThyrotoxicosis facticia (0.2%)Metastatic thyroid carcinoma (0.1%)Struma ovarii

  • CLINICAL FEATURES OF HYPERTHYROIDISMMost signs and symptoms are common to all types of thyreotoxicosis;Some of them are specific to defined diseasefor example:ophthalmopathypretibial myxoedemathyroid acropathyGravesdiseasethyroid paintenderneessubacutethyroiditis

  • CLINICAL FEATURES OF HYPERTHYROIDISM(according to frequency)SYMPTOMSNervousnessPalptationsIncreased sweatingHaet intoleranceFatigueWeight lossDyspneaIncreased appetiteEye symptomsFriable hair and nailsIncreased bowel movementsDiarrhoeaMenstrual disturbancesSIGNSTachycardiaGoitreTremorsSkin changesHyperkinesisThyroid bruitLid lag and retractionOphthalmopathyAtrial fibrillationOnycholisisLocalized (pretibial) myxedemaVitiligoAcropathy

  • GRAVES DISEASEthe most frequent cause of hyperthyroidismGraves disease is an autoimmune thyroid disease, characterized by diffuse thyroid enlargement, ophtalmopathy and less frequently dermopathy (pretibial myxedema) and acropathy.It can occur at any age (unusual before puberty and most commonly affects the 30-50- years-old age group)the female/ male ratio ~7 : 1

  • Graves disease - pathogenesisThyroid antigen-specific T lymphocytesHumoral and cell-mediated immune reactionsInfiltration of the thyroid gland by immune effector cells

  • Graves disease - pathogenesisGenetic and environmental factorsProduction of IgG antibodies(thyroid-stimulating immunoglobulins TSIor TSH-receptor antibodies TRAb)Stimulation thyroid hormone production and goitre formation

  • Graves disease - pathogenesisGenetic factors:The familial predisposition.The frequent finding of circulating autoantibodies in relatives of Graves patients.The high concordance rate in monozygotic twins.The positive association with haplotypes HLA-B8 and DR3 (Caucasians), HLA-B35 (Japonese population), and HLA-Bw46 (Chinese population).Female sex hormones.

  • Graves disease - pathogenesisEnvironmental factors:IodineImmune-stimulant effect(in areas of iodine defficiency thyroid autoimmune diseases are rare). Cigarettes(assotiation with Graves ophtalmopathy influence on immune-competent cells?).

  • Graves disease - pathogenesisEnvironmental factors:Escherichia coli and Yersinia enterocolitica(antibodies to these microbial antigenscross-reaction with the TSH-receptorhyperthyroidism.Stress(relationship between the onset of hyperthyroidism and a major life event).

  • Graves disease - pathogenesisOphtalmopathy and dermopathy:Pathogenesis is less well understood.Immunologically mediated but TRAb is not implicated.

    Proliferation of fibroblasts (adipocytes?) within the orbitIncreased interstitial fluid contentChronic inflammatory cel infiltrateSwelling of the extra-ocular muscles Rise in retrobulbar pressure

  • Graves disease - clinical findingsTHYROID GLAND: Symmetrically enlargedFirmThrills and bruits

    Goiter is absent in 3% of causes

  • Graves disease clinical findingsLOCALIZED MYXEDEMA: Pretibial regionRaised, light colored or yellow-reddish lesion with orange peel apperanceSometimes pruritus

  • Graves disease clinical findingsTHYROID ACROPATHY: Swelling and soft tissues of hands feetClubbing of fingers and toes

  • True ophtalmopathy is specific of Graves diseaseSoft tissue involvement:Lacrimation RednessBurning sensation PhotophobiaGritty sensationProptosis (exophtalmos) and lagophthalmoskeratitisExtra-ocular muscle dysfunctiondiplopiaOptic neuropathyblidness

  • Cardiovascular systemTachycardiaPalpitationsBlood pressure:systolic diastolic

    THYROCARDIAC SYNDROMEPremature heart beatsAtrial fibrillationHeart failure and/or angina

  • Alimentary systemIncreased appetitebut weight lossIncreased frequency of bowel movements and diarrheaRarely liver dysfunction

  • Nervous systemNervousnessAnxietyEmotional instability

    HyperactivityInsomniaFine tremorsMusclesMuscular weaknessIn most severe cases muscular atrophy

  • Skeletal systemMetabolismIncreased oxygen consumptionDiabetes mellitus may be exacerbatedSerum cholesterol plasma triglycerides

    ThyrotoxicosisIncreasedloss of boneosteoporosis

  • GRAVES DISEASE DIAGNOSTIC PROCEDURESLabolatory investigationimportant particularly in the absence of goitre and eye diseaseImaging studiesImportant particularly in diagnostic of Graves ophtalmophathyComputed tommographyMagnetic resonance

  • LABORATORY INVESTIGNATIONHyperthyroidism

    Serum concentrations of:TSH: undetectable or FT4: FT3:

    T3-toxicosis: TSH: undetectable or FT3: FT4: Graves disease:TRAb TPO ATG

  • Imaging studies24-hour thyroidal radioactive iodine uptake:increasedthyroid scan diffuse, homogenous goitreThyroid ultrasound:enlarged glandhypoechoic patternincreased blood flowComputed tomography and magnetic resonance

  • GRAVES DISEASE TREATMENTGeneral principles of treatment Treatments available for Graves diseaseMEDICALSURGICALRADIOIODINEMost treatment regiments are directed at the thyroid, but there is a small place for peripherally acting drugs such as propranolol and ipodate.

  • GRAVES DISEASE TREATMENTPatient preferenceSmall goitreMild diseaseOther diseasesChildrenPregnancyOphtalmopathyPreoperativePre-radioiodineThyrotoxic crisisRelapse after thyroidectomyIndications for medical treatment

  • ANTITHYROID DRUGSTHIONAMIDES:Methimazole, Carbimazole, Propylthiouracil

    Mechanism of actions:Inhibition of thyroid hormone synthesis and secretionPTUinhibition of peripheral conversion of T4 to T3

  • THIONAMIDESGoal:Permanent remission of hyperthyroidismLimitations:High recurrence rate of hyperthyroidismPossible side effects

  • Factors that may influance antithyroid drug therapyassociated with remissionClinicalSmall goitreMild diseaseRapid responce to antithyroid drugsSmall maintenance doseFemale sexLow iodine intakeLaboratoryModest elevation of thyroid hormonesLow urinary iodine excretionLow or absent TSH-R9s) antibodies at end of therapyNormal responce to TRH at end of therapyNormal suppression of thyroidal radioiodine uptake at end of therapy

  • Factors that may influance antithyroid drug therapyassociated with relapseClinicalLarge goitreVascular goitreSevere diseaseSlow responce to antithyroid drugsLarge maintenance doseMale sexHigh iodine intakeLaboratoryMajor elevation of thyroid hormonesHigh urinary iodine excretionRaised TSH-R(s) antibodies at end of therapyAbsent responce to TRH at end of therapyImpaired or absent suppression of thyroidal radioiodine uptake at end of therapy

  • THIONAMIDESNauseaVomitingPruritisSkin rashUrticariaLoss of tasteSide effects(overall frequency
  • GRAVES DISEASE TREATMENTExperienced thyroid surgeon avaliablePatient preferenceAdults up to 40 yearsSevere diseaseNodular goitreLarge goitreRelapse after drug treatmentIndications for surgical treatment

  • SURGICAL TREATMENTPARTIAL THYROIDECTOMYMechanism of actionremoval of tissue responsible for excessive thyroid hormone synthesis

  • PARTIAL THYROIDECTOMYGoalthyroid ablation, i.e. hypothyroidism

    Contraindicationssystemic contraindications to surgery

  • PARTIAL THYROIDECTOMY- COMPLICATIONS

    EARLYRecurrent laryngeal nerve palsySuperior laryngeal nerve palsyHaemorrhageHypoparathyroidismPneumothoraxThyroid crisisDamage to thoracic drugDamage to carotic arteryDamage to jugular veinLATECheloid scarTethered scarHypothyroidismRecurrence of hyperthyroidismRecurrent upper pole nodules

  • GRAVES DISEASE TREATMENTPatient preferencePoor-compliance with antithyroid drugsPatients over 40 yearsRecurrence after thyroidectomy

    Severe uncontrolled diseaseLarge goitreUnco-operative patientsPresence of other disease(s)Indications for radioiodine therapy

  • RADIOIODINE THERAPYMechanism of actionDestruction of thyrocytes by -radiation

    Goalthyroid ablation, i.e. hypothyroidism

    Contraindicationspregnancy

  • RADIOIODINE THERAPYComplcationsPermanent hypothyroidismTransient hypothyroidismThyroiditisSialadenitisThyrotoxic crisisNodule formationPossible exacerbation of ophtalmopathy (preventable by glucocorticoids)

  • GRAVES DISEASE TREATMENT-adrenergic antagonists (e.g. Propranolol)Inorganic iodidePotassium perchlorateGlucocorticoidsOther drugs

  • GRAVES DISEASE TREATMENT OF OPHTHALMOPATHY

    Mild ophthalmopathyGuanethidine or -adrenergic eye drops (lid retraction)Methylcellulose eye drops (lacrimation, burning sensation)Sunglasses (photophobia)Nighttime tapering of eyes (lagophthalmos)Prisms (mild diplopia)

  • Severe ophthalmopathyHigh-dose glucocorticoids (active ophthalmopathy)Orbital radiotherapy(active ophthalmopathy)Orbital decompresion(active or inactive ophthalmopathy)Rehabilitative surgery: eye muscles, eyelids (to be performed at least 6 months after rendering ophthalmopathy stable and inactive with other treatments)Immunosuppressive drugs, somatostatin analogues, intravenous immunoglobulins, plasmapheresis.

  • THYROTOXIC STORMRARE BUT VERY SERIOUS COMPLICATION OF HYPERTHYROIDISM

    Severe manifestations of hypermetabolic(fever, profound sweating, dehydration, restlessness, insomnia)In patients with not diagnosed or inadeguately treated hyperthyroidismSURGERYINFECTIONSTRAUMASTHYROTOXIC STORM

  • THYROTOXIC STORM - TREATMENTHigh doses of thionamideIodide or iodinated contrast agentsGlucocorticoids -adrenergic antagonists The treatmnent of underlying non-thyroidal illnessCorrection of dehydrationNormalisation of body temperaturePlasmapheresis or peritoneal dialysis

  • TOXIC ADENOMAAn autonomously functioning, benign thyroid nodule causing thyrotoxicosisFREQUECYIodine-deficientareasIodine-sufficient areas10%>10%

  • TOXIC ADENOMAotherwise normal thyroid glandgoiterSolitary nodule in:Pathogenesis:Somatic mutations in the gene encoding the TSH receptorconstitutive activation of TSH receptor

  • TOXIC ADENOMASmptoms and signs of thyrotoxicosis Ophthalmopathy, localized myxedema and acropachy are absent

    Thyroid scanPrevalent tracer uptake in the nodule(hot nodule)

    TreatmentRadioiodine or surgeryAntithyroid drugs only for preparation of definitive treatment

  • TOXIC MULTINODULAR GOITERMultiple hyperfunctioning thyroid nodules or areas of autonomously functioning thyroid follicles

    Commonly found in older patients with long-standing multinodular goiter.

  • UNUSUAL FORMS OF THYROTOXICOSISTSH-secreting pituitary adenoma(280 cases so far described)TSH or ; FT4 ; FT3 TSH -subunit TSH -subunit / TSH>1Selective pituitary resistenceTSH or ; FT4 ; FT3 TSH -subunit TSH -subunit / TSH
  • UNUSUAL FORMS OF THYROTOXICOSISThyrotoxicosis factitia

    Clinical and biochemical picture is typical of thyrotoxicosisGoiter is absentRAIU is very low/suppressedSerum thyroglobulin very low or undetectableCongenital hyperthyroidismGermline mutations of the TSH-R geneConstitutional activation in all thyroid follicular cells

  • UNUSUAL FORMS OF THYROTOXICOSISMetastatic thyroid carcinoma

    Follicular thyroid arcinomaMetastases to lung and boneThyrotoxicosis (rarely)Struma ovariiFunctioning thyroid tissue within an ovarian teratoma or dermoid

  • UNUSUAL FORMS OF THYROTOXICOSISTrophoblastic tumors

    High serum and urine concentrations of -subunit of chorionic gonadotropinstimulation of TSH receptor