Textbook reading Thyroid imaging function studies function studies Radioiodine therapy 蔡碧瑜...

Textbook readingTextbook reading

Thyroid imaging Thyroid imaging function studiesfunction studies

Radioiodine therapyRadioiodine therapy

蔡碧瑜李永隆陳修弘蔡碧瑜李永隆陳修弘

Thyroid imaging and function Thyroid imaging and function studiesstudies

Evaluation for clinical palpable Evaluation for clinical palpable nodulesnodules

• Thyroid scintigraphy and radiotracer Thyroid scintigraphy and radiotracer uptake studiesuptake studies

• U.S. and F.N.AU.S. and F.N.A

• Laboratory dataLaboratory data

Thyroid scintigraphyThyroid scintigraphy

• Determining the Determining the functional statusfunctional status of of the thyroid nodules.the thyroid nodules.

• Detection of the Detection of the extra-thyroid extra-thyroid metastasismetastasis form thyroid carcinoma. form thyroid carcinoma.

• The thyroid tissue origins from The thyroid tissue origins from mediastinal massesmediastinal masses..

• Correcting the physical finding with Correcting the physical finding with abnormalities in the image.abnormalities in the image.

RadiopharmaceuticalsRadiopharmaceuticals

• Iodine-131Iodine-131

• Iodine-123Iodine-123

• Technetium-99mTechnetium-99m

RadiopharmaceuticalsRadiopharmaceuticals

Iodine Iodine • a precursor of a precursor of

thyroid hormone .thyroid hormone .• concentration concentration

(100:1 than (100:1 than plasma)plasma)

• Organification.Organification.• Bound to Bound to

thyroglobulin.thyroglobulin.

Pertechnetate Pertechnetate ion (TcO4-)ion (TcO4-)

• concentrationconcentration

Physics and dosimetryPhysics and dosimetryiodine-131iodine-131

Iodine-131Iodine-131

not good choice for routine thyroid not good choice for routine thyroid scintigraphyscintigraphy

• The presence of beta particle The presence of beta particle emissionsemissions

• The relative high energy of the The relative high energy of the principal gamma ray emissions for principal gamma ray emissions for gamma camera.gamma camera.

• The long half-life The long half-life

Physics and dosimetryPhysics and dosimetryiodine-123iodine-123


Better for thyroid imageBetter for thyroid image• Electron captureElectron capture

• Gamma energy is ideally suited for Gamma energy is ideally suited for gamma camera(159 keV)gamma camera(159 keV)

• Half-life is suitable (13.2hr)Half-life is suitable (13.2hr)


DisadvantageDisadvantage

• Prepared from I-124 and I-125Prepared from I-124 and I-125

• Higher radiation precursorsHigher radiation precursors

• Short half-life Short half-life

• Commercial limitedCommercial limited

• Higher costHigher cost

Physics and dosimetryPhysics and dosimetryTechnetium-99mTechnetium-99m

Technetium-99mTechnetium-99m

• Better for thyroid scintigraphyBetter for thyroid scintigraphy

• Reliably available from molybdenum-Reliably available from molybdenum-99 /Tc99m generator system99 /Tc99m generator system

• Ideal half-life (6hr)Ideal half-life (6hr)

• Suitable energy (only gamma ray Suitable energy (only gamma ray 140KeV)140KeV)

PharmacokineticsPharmacokineticsradioiodineradioiodine

• GI absorbs ion by Oral administrationGI absorbs ion by Oral administration• Into circulationInto circulation• Rapid uptake and Organification of Rapid uptake and Organification of

iodineiodine• Detectable within Detectable within minutes.minutes.• Reached the follicular lumen within Reached the follicular lumen within 20-20-

30 minutes30 minutes• Normal range for uptake is Normal range for uptake is 10%-30%10%-30% of of

the administered dose at 24 hrthe administered dose at 24 hr

PharmacokineticsPharmacokineticsradioiodineradioiodine

I-123I-123• Detection after Detection after

several several hourshours delaydelay

I-131I-131

• Detection after Detection after 1 1 dayday delay delay

PharmacokineticsPharmacokineticsTechnetium-99mTechnetium-99m

• IvIv administration administration

• Rapid uptake by thyroid but not Rapid uptake by thyroid but not organificationorganification

• Optimal uptake for imaging is 20-30 Optimal uptake for imaging is 20-30 min with the 0.5-3.75% of the min with the 0.5-3.75% of the reagentreagent

Technetium-99m & Technetium-99m & radioiodineradioiodine

• Concordant localization and identical scConcordant localization and identical scintigraphyintigraphy

• Dis-concordantDis-concordant in a small percentage of in a small percentage of thyroid nodules for the thyroid nodules for the loss of the organiloss of the organificationfication

PrecautionsPrecautions

• Breast feedingBreast feeding

• PregnancyPregnancy

• Interference of stable iodine Interference of stable iodine contained in foods and medicationscontained in foods and medications

Breast feedingBreast feeding

I-123I-123• Resumed after several days if the amount used Resumed after several days if the amount used

if no more than 30 uCi usedif no more than 30 uCi used• Usual imaging dosage is 100-400 uCi Usual imaging dosage is 100-400 uCi I-131I-131• Should be terminated for several weeksShould be terminated for several weeksTc99m pertechnetateTc99m pertechnetate• Resumed in 24 hrResumed in 24 hr

radioiodine radioiodine precaution for pregnancyprecaution for pregnancy

• Radioiodine can cross placentaRadioiodine can cross placenta

• Fetal thyroid can concentrate iodine Fetal thyroid can concentrate iodine after after 1010thth -12 -12thth gestation weeks. gestation weeks.

• Resulting in hypothyroidism and Resulting in hypothyroidism and cretinism.cretinism.

Interference for radioiodine Interference for radioiodine uptakeuptake

• Several non-iodine drug can affect Several non-iodine drug can affect that.that.

• 1 mg1 mg of stable iodine can cause of stable iodine can cause significant reduction of the 24 hr significant reduction of the 24 hr radioiodine uptakeradioiodine uptake

• 10 mg10 mg can effectively block the can effectively block the gland, with 98% reduction uptake.gland, with 98% reduction uptake.

Normal thyroid scintigraphyNormal thyroid scintigraphy

• In the euthyroid adult the thyroid In the euthyroid adult the thyroid gland weights gland weights 15-20 g15-20 g..

• Butterfly shape with lateral lobe Butterfly shape with lateral lobe extending along each side of the extending along each side of the thyroid cartilagethyroid cartilage of the larynx of the larynx

• The lateral lobes are connected by The lateral lobes are connected by an isthmus that crosses the trachea an isthmus that crosses the trachea anteriorly anteriorly below the level of the below the level of the cricoid cartilage.cricoid cartilage.

• The The right loberight lobe is often larger than the is often larger than the left.left.

• The lateral lobes typically measure The lateral lobes typically measure 4-5 4-5 cmcm from superior to inferior poles and from superior to inferior poles and 1.5-2 cm1.5-2 cm wide. wide.

• The The pyramidal lobepyramidal lobe is a paramedian is a paramedian structure that arises from thestructure that arises from the isthmus isthmus, , either to the right or left lobe of the either to the right or left lobe of the middle, and represents functioning middle, and represents functioning thyroid tissue in the thyroid tissue in the thyroglossal duct thyroglossal duct tracttract..

Normal thyroid scintigraphyNormal thyroid scintigraphy

• HomogeneousHomogeneous

• Uniform distributionUniform distribution

• VariationVariation– Middle or medial of the lateral lobes Middle or medial of the lateral lobes

owing to the thickness owing to the thickness – Activity of the Isthmus varies greatly Activity of the Isthmus varies greatly

among patients, with among patients, with little or no activitylittle or no activity and prominent activityand prominent activity

TC-99m pertechnetateTC-99m pertechnetate

• Thyroid tissue Thyroid tissue

• Salivary gland Salivary gland

• Esophagus activity seen to the left of Esophagus activity seen to the left of middle and can confirm by having middle and can confirm by having patient swallow, hollowed by a patient swallow, hollowed by a repeat image.repeat image.

Clinical applicationsClinical applications

indication for thyroid scintigraphyindication for thyroid scintigraphy• Further evaluation of findings on physical Further evaluation of findings on physical

examinationexamination• Detection ofDetection of metastases metastases with thyroid carcinoma with thyroid carcinoma• Follow-upFollow-up of radioiodine therapy for differentiated of radioiodine therapy for differentiated

thyroid cancerthyroid cancer• Determination of functional status of thyroid Determination of functional status of thyroid

nodules nodules • Differential diagnosis of mediastinal massesDifferential diagnosis of mediastinal masses• Detection of Detection of extra thyroidal tissue (lingual extra thyroidal tissue (lingual

thyroid)thyroid)• Screening after dead and neck irradiation.Screening after dead and neck irradiation.

Clinical applicationsClinical applicationsGoiterGoiter• Refers to an enlargement of the thyroid glandRefers to an enlargement of the thyroid gland• Endemic goiters Endemic goiters

– Iodine deficiency-induced hyperplasiaIodine deficiency-induced hyperplasia– Colloid nodular goitersColloid nodular goiters– Nontoxic goitersNontoxic goiters

• Graves’ diseaseGraves’ disease– Toxic goiterToxic goiter

• Thyroid carcinomaThyroid carcinoma• Other neoplasm-lymphomaOther neoplasm-lymphoma• Active phase of thyroiditisActive phase of thyroiditis

Scintigraphy of GoiterScintigraphy of Goitermultinodular colloid goiters multinodular colloid goiters

• Inhomogeneous uptake of tracer Inhomogeneous uptake of tracer

• Cold areas of various sitesCold areas of various sites

• Carcinoma changes rate is low (1-Carcinoma changes rate is low (1-5%)5%)– Highly suspicion: out of proportion in Highly suspicion: out of proportion in

size to other cold areas or enlarging size to other cold areas or enlarging suddenly.suddenly.

Scintigraphy of GoiterScintigraphy of GoiterGraves’ diseaseGraves’ disease

• UniformUniform with intensely increased uptake with intensely increased uptake• The The pyramidal lobepyramidal lobe is frequently seen is frequently seen• Not generally considered an indication fNot generally considered an indication f

or obtaining a thyroid scinitigram (?)or obtaining a thyroid scinitigram (?)

Clinical applicationsClinical applicationsthyroid nodulesthyroid nodules

• Extremely common Extremely common

• The incidence increases with ageThe incidence increases with age

• More common in womenMore common in women

• Likehood of Likehood of malignancymalignancy::– Multiple noduleMultiple nodule (multiple nodular (multiple nodular

goiters, less than 5%)goiters, less than 5%)– Solitary cold nodule (5-40%)Solitary cold nodule (5-40%)

Scintigraphy for thyroid Scintigraphy for thyroid nodulesnodules• Cold nodules-nonfunctioningCold nodules-nonfunctioning

– The majority of the thyroid nodulesThe majority of the thyroid nodules– As small as As small as 3 cm3 cm can be detected by pinhole collimator can be detected by pinhole collimator

• Hot nodules-functioningHot nodules-functioning– Function equal to the surrounding normal thyroidFunction equal to the surrounding normal thyroid

• IndeterminateIndeterminate– Need to close to correct between physical examination and Need to close to correct between physical examination and

scintigraphy findings.scintigraphy findings.– Oblique view with a pinhole collimatorOblique view with a pinhole collimator– The management is the same as the cold nodules.The management is the same as the cold nodules.

Cold nodulesCold nodules

Risk factors of malignancyRisk factors of malignancy• prior history of radiation to the head anprior history of radiation to the head an

d neck or mediastinumd neck or mediastinum– >1000-1500 rads>1000-1500 rads

• Solitary cold nodules in young femaleSolitary cold nodules in young female• Multiple nodular goiters in elderlyMultiple nodular goiters in elderly

Hot nodulesHot nodules

• Hyper functioningHyper functioning

• AutonomousAutonomous

• Out of negative feedback controlOut of negative feedback control


• Autonomous nodulesAutonomous nodules– Thyroid gland produces much hormoneThyroid gland produces much hormone– Greater than Greater than 3-4 cm3-4 cm

•suppress pituitary TSHsuppress pituitary TSH•Extra-nodular thyroid tissue is not visualableExtra-nodular thyroid tissue is not visualable

– Small nodulesSmall nodules•Extra-nodular thyroid tissue is visualableExtra-nodular thyroid tissue is visualable

– Spontaneous involutionSpontaneous involution•Cystic degenerationCystic degeneration


• Hot nodules with hyperthyroidismHot nodules with hyperthyroidism– Large(3-4 cm), multiple nodulesLarge(3-4 cm), multiple nodules

• Autonomous hot nodule with Autonomous hot nodule with ThyrotoxicosisThyrotoxicosis– Plummer’s diseasePlummer’s disease

Discordant nodulesDiscordant nodules

• Possibility of discordant between Possibility of discordant between radioiodine and Tc-99m radioiodine and Tc-99m pertechnetatepertechnetate– Radioiodine-coldRadioiodine-cold– Tc-99m pertechnetate-hotTc-99m pertechnetate-hot

• 2-3 % in Tc-99m pertechnetate hot 2-3 % in Tc-99m pertechnetate hot nodulesnodules

Substernal thyroidSubsternal thyroid

D.D mediastinal massesD.D mediastinal masses• Goitrous enlargement with downward eGoitrous enlargement with downward e

xtension xtension • Abnormal migration during develop Abnormal migration during develop

Substernal thyroidSubsternal thyroid

• I-131I-131 is better than Tc99m is better than Tc99m• DelayedDelayed performed (48-72 hr) performed (48-72 hr)

– Function and tracer uptake in sternal thyroiFunction and tracer uptake in sternal thyroid is poord is poor

– Blood clearance of the background activityBlood clearance of the background activity• Cervical thyroidCervical thyroid should also be noted should also be noted

Clinical applicationsClinical applicationsother ectopic thyroid tissueother ectopic thyroid tissue

• The The thyroglossal ductthyroglossal duct runs from the runs from the foramen cecumforamen cecum at the at the base of the tonguebase of the tongue to the thyroid to the thyroid

• Lingual thyroidLingual thyroid –complete failure to –complete failure to migratemigrate

• Absence of tracer uptake in the expected Absence of tracer uptake in the expected cervical areacervical area

• Thyroid tissue may be found along the Thyroid tissue may be found along the tract of the thyroglossal duct.tract of the thyroglossal duct.

Clinical applicationsClinical applicationsthyroiditisthyroiditis• Acute thyroiditisAcute thyroiditis

– Suppurative bacterial infectionSuppurative bacterial infection– Focal abscessFocal abscess

• subacute thyroiditissubacute thyroiditis– Granulomatous thyroiditisGranulomatous thyroiditis– De Quervain’s diseaseDe Quervain’s disease– Non-suppurative Non-suppurative – Etiology unproved-virus infection (URI, neck tenderness)Etiology unproved-virus infection (URI, neck tenderness)– Initial phase would be a ThyrotoxicosisInitial phase would be a Thyrotoxicosis

• Chronic thyroiditisChronic thyroiditis– Hashimoto’s thyroiditisHashimoto’s thyroiditis– Lymphocytic infiltrationLymphocytic infiltration– More common in women with goiter or hypothyroidismMore common in women with goiter or hypothyroidism– Rarely with hyperthyroidism-hashitoxicosisRarely with hyperthyroidism-hashitoxicosis

Scintigraphy for acute & Scintigraphy for acute & subacute thyroiditissubacute thyroiditis

• Acute thyroiditisAcute thyroiditis– Cold noduleCold nodule for the focal abscess for the focal abscess

• Subacute thyroiditisSubacute thyroiditis– Decrease or absent uptakeDecrease or absent uptake of of

radioiodine in the affected part of the radioiodine in the affected part of the glandgland

– Gallium-67Gallium-67 imaging :inflammatory imaging :inflammatory processprocess

Scintigraphy for chronic Scintigraphy for chronic thyroiditisthyroiditis

• Highly variable and depend on the Highly variable and depend on the stage in the natural history stage in the natural history

• Normal in the early stageNormal in the early stage

• Later, diffuse enlargement Later, diffuse enlargement

• Eventually, hypothyroidism, Eventually, hypothyroidism, inhomogeneous with hot and cold inhomogeneous with hot and cold areasareas

Clinical applicationsClinical applicationsthyroid cancer metastasisthyroid cancer metastasis

• Follicular carcinomaFollicular carcinoma

• Mixed papillary-follicular carcinomaMixed papillary-follicular carcinoma

• Papillary carcinomaPapillary carcinoma

• Medullary carcinomaMedullary carcinoma

• Ana plastic carcinomaAna plastic carcinoma

Thyroid cancer metastasisThyroid cancer metastasis

• The most common sites of The most common sites of metastasis are locally in the metastasis are locally in the lymph lymph nodes of the neck, lung ,and bone.nodes of the neck, lung ,and bone.

• nodal activity is nodal activity is focal ,intense, focal ,intense, starburst patternstarburst pattern on parallel-hole on parallel-hole collimatorscollimators

Thyroid cancer metastasisThyroid cancer metastasis

• Imaging is performed Imaging is performed 48-72 hr48-72 hr after after radioiodine administration.radioiodine administration.

• More lesion are demonstrated in this More lesion are demonstrated in this time than at 24 hr.time than at 24 hr.

I-131 follow-up imagingI-131 follow-up imaging

The preparations and dosage are The preparations and dosage are controversial.controversial.

• Thyroid hormone replacement is withdraw for Thyroid hormone replacement is withdraw for 4-6 weeks4-6 weeks to stimulate TSH secretion. to stimulate TSH secretion.

• Use bovine TSH before imaging.Use bovine TSH before imaging.– Not satisfactory for increasing I-131 uptakeNot satisfactory for increasing I-131 uptake– allergyallergy

Scanning dosages for follow-up Scanning dosages for follow-up imagingimaging

• ControversialControversial

• More metastasis deposits are seen with More metastasis deposits are seen with higher doseshigher doses

• 5-10 mCi of I-1315-10 mCi of I-131 for detecting metastasis for detecting metastasis

• As little as 5 mCi with less satisfactory As little as 5 mCi with less satisfactory uptake of sequent therapeutic dose uptake of sequent therapeutic dose

• Diagnostic dose should be Diagnostic dose should be limited 1-2 mCilimited 1-2 mCi

Tumor imagingTumor imaging

• Thalium-201 chlorideThalium-201 chloride

• Tc-99m sestamibiTc-99m sestamibi

• For location metastasis in patients For location metastasis in patients with with increased thyroglobulinincreased thyroglobulin and and negative radioiodinenegative radioiodine whole body whole body scintigraphyscintigraphy

Iodine -131 MIBG for Medullary Iodine -131 MIBG for Medullary carcinomacarcinoma

• meta-iodo-benzyl-guanidinemeta-iodo-benzyl-guanidine• Neurosecretory storage vesicles of Neurosecretory storage vesicles of chrochro

maffin cellsmaffin cells• Sensitivity is low (30%)Sensitivity is low (30%)• Soft tissue metastasis is more visualized Soft tissue metastasis is more visualized

than bone metastasis.than bone metastasis.

Medullary carcinoma of Medullary carcinoma of thyroidthyroid• Indium -111 somatostatin receptor Indium -111 somatostatin receptor

scintigraphy for Medullary carcinomascintigraphy for Medullary carcinoma

• Iodine -131 MIBGIodine -131 MIBG

• FDG-PETFDG-PET

Thyroid function studiesThyroid function studies

• Thyroid percent uptakeThyroid percent uptake• Suppression testSuppression test• Stimulation testStimulation test• Per chlorate discharge testPer chlorate discharge test

Thyroid percent uptakeThyroid percent uptake

• The earliest applications radiotracer The earliest applications radiotracer in medicine.in medicine.

• The degree of radioiodine uptake The degree of radioiodine uptake parallels the functional activities of parallels the functional activities of the thyroid hormone producedthe thyroid hormone produced

• Normal uptake range Normal uptake range 10-30%10-30%• Sensitivity and specific test of serum Sensitivity and specific test of serum

T3 T4T3 T4

Thyroid percent uptakeThyroid percent uptake

• DD hyperthyroidismDD hyperthyroidism– Increase uptakeIncrease uptake

•Graves’ diseaseGraves’ disease

•Plummer’s diseasePlummer’s disease

– Decrease uptakeDecrease uptake•Subacute thyroiditisSubacute thyroiditis

•Thyrotoxicosis factitiaThyrotoxicosis factitia

Suppression testSuppression test

• Not used in current routine practice.Not used in current routine practice.

• Autonomous functioning glandsAutonomous functioning glands

• TSHTSH level is a sensitivity test now level is a sensitivity test now

Suppression testSuppression test

• Receiving 25 mg Receiving 25 mg T3T3 qid for 8 day qid for 8 day• 24hr uptake is repeated beginning at 724hr uptake is repeated beginning at 7thth

day.day.• It is It is fall in the percentage of uptakefall in the percentage of uptake to le to le

ss 50% of the baseline and less the 10% ss 50% of the baseline and less the 10% overall.overall.

Stimulation testStimulation test

• Infrequent use now.Infrequent use now.

• D.D primary and secondary D.D primary and secondary (pituitary) hypothyroidism(pituitary) hypothyroidism– PrimaryPrimary-failure to response to -failure to response to

exogenous TSHexogenous TSH– SecondarySecondary-increasing radioactivity after -increasing radioactivity after

TSH administrationTSH administration

Stimulation testStimulation test

• Receiving 10 units of TSH ivReceiving 10 units of TSH iv

• The radiotracer repeats beginning The radiotracer repeats beginning the next day.the next day.

• Primary-no responsePrimary-no response

• Secondary-radiotracer doublingSecondary-radiotracer doubling

Per chlorate discharge testPer chlorate discharge test

• to detect defects into detect defects in

Intra-thyroidal iodide Intra-thyroidal iodide organificationorganification


• Dissociation of the trapping and organifiDissociation of the trapping and organification functioncation function – Congenital enzyme deficiency associated wiCongenital enzyme deficiency associated wi

th deafness (Pendred's syndrome), th deafness (Pendred's syndrome), – Some chronic thyroiditisSome chronic thyroiditis– During the treatment of PTUDuring the treatment of PTU


• I is "I is "trappedtrapped" by the thyroid gland " by the thyroid gland through an energy-requiring through an energy-requiring active active transporttransport mechanism mechanism

• Once in the gland, it is rapidly Once in the gland, it is rapidly bound bound to thyroglobulin to thyroglobulin


• inhibit active iodiinhibit active iodide transportde transport

• cause the release of tcause the release of the intrathyroidal iodihe intrathyroidal iodide not bound to thyrde not bound to thyroid proteinoid protein

• thiocyanate (SCthiocyanate (SCN-) N-)

• perchlorate (ClOperchlorate (ClO4-4-))

•


• administration of administration of radioiodineradioiodine orally orally• counts are obtained at frequent intervalcounts are obtained at frequent interval

s (every 10 or 15 minutes). s (every 10 or 15 minutes). • Two hours later, Two hours later, 1g of KClO41g of KClO4 orally orally• repeated epithyroid counts continue to repeated epithyroid counts continue to

be obtained for an additional 2 hours be obtained for an additional 2 hours

In normal individualsIn normal individuals

• little loss of the thyroidal radioactivity alittle loss of the thyroidal radioactivity accumulated prior to induction of the "trccumulated prior to induction of the "trapping" block apping" block

• radioiodine accumulation in the thyroid radioiodine accumulation in the thyroid gland ceases after the administration of gland ceases after the administration of the iodide transport inhibitor the iodide transport inhibitor


• Less than 10% discharge of radioiodine:Less than 10% discharge of radioiodine:– NormalNormal– Hyperthyroidism on inadequate antithyroid Hyperthyroidism on inadequate antithyroid

drug therapydrug therapy• Greater than 10% washout:Greater than 10% washout:

– Organification defectOrganification defect

Radioiodine treatmentRadioiodine treatment

• Hyperthyroidism Hyperthyroidism

• Thyroid cancerThyroid cancer

HyperthyroidismHyperthyroidismindications for iodine-131 indications for iodine-131 therapytherapy• Graves’ disease (diffuse toxic goiter)Graves’ disease (diffuse toxic goiter)

• Plummer’s disease (toxic nodular Plummer’s disease (toxic nodular goiter)goiter)

• Functioning thyroid cancer Functioning thyroid cancer (metastasis)(metastasis)

HyperthyroidismHyperthyroidism Contraindication for iodine-131 Contraindication for iodine-131 therapytherapy• Thyrotoxicosis factitiaThyrotoxicosis factitia• Subacute thyroiditisSubacute thyroiditis• Silent thyroiditis (atypical ,subacute, lymphocytic, Silent thyroiditis (atypical ,subacute, lymphocytic,

transient, postpartum)transient, postpartum)• Struma ovariiStruma ovarii• Thyroid hormone resistanceThyroid hormone resistance• Secondary hyperthyroidismSecondary hyperthyroidism• Thyrotoxicosis associated with Hashimoto’s disease Thyrotoxicosis associated with Hashimoto’s disease

(hashitoxicosis)(hashitoxicosis)• Jod-Basedow phenomenon (iodine-induced Jod-Basedow phenomenon (iodine-induced

hyperthyroidism)hyperthyroidism)


• GoalGoal– EuthyroidEuthyroid in a reasonable length of time wit in a reasonable length of time wit

h a single radioiodine doseh a single radioiodine dose– Graves’diseas-80-120 uCi/gGraves’diseas-80-120 uCi/g

•Standard dose:5-10mCiStandard dose:5-10mCi•Higher for Graves’ opthalmopathyHigher for Graves’ opthalmopathy

– More than More than 90%90% patients are cured with a sin patients are cured with a single dosegle dose

– Hypothyroidism-hormone replacementHypothyroidism-hormone replacement


• Plummer’s diseasePlummer’s disease– Hyperthyroidism caused by toxic nodulesHyperthyroidism caused by toxic nodules– More radio-resistantMore radio-resistant– Inhomogenity, rapidly radioiodine turnover ,Inhomogenity, rapidly radioiodine turnover ,

low retain doselow retain dose– Increase dose to 15-29 mCiIncrease dose to 15-29 mCi


• Metastases from differentiated Metastases from differentiated thyroid cancerthyroid cancer

• Controversial with small , early stage Controversial with small , early stage lesionslesions

• Residual, recurrence differentiatedResidual, recurrence differentiated thyroid cancer - improved survival thyroid cancer - improved survival rate with I-131rate with I-131


• Metastasis more common at neck, Metastasis more common at neck, lung and bonelung and bone

• Bone metastasis is more difficult Bone metastasis is more difficult eradicated than lung metastasiseradicated than lung metastasis

• Initial dose 150-200mCiInitial dose 150-200mCi

• Repeated doses up to 1CiRepeated doses up to 1Ci


• Follow-up imaging is performed yearly uFollow-up imaging is performed yearly until the metastatic lesions are eliminationtil the metastatic lesions are eliminationn

• Serum thyroglobulinSerum thyroglobulin –tumor marker –tumor marker– If the level is increase in a post-op patient. it If the level is increase in a post-op patient. it

may be a recurrencemay be a recurrence– Then performed imaging to localize the lesiThen performed imaging to localize the lesi

onon


• Not statistically significances of leading Not statistically significances of leading the secondary cancer by radioiodine Txthe secondary cancer by radioiodine Tx

• Not reduce fertilityNot reduce fertility• Congenital defects are not increased in tCongenital defects are not increased in t

he child of treated patientshe child of treated patients

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