Radioiodine Therapy for Graves’ Radioiodine Therapy for Graves’ DiseaseDisease

Dr. Khalid B. MakhdomiDr. Khalid B. Makhdomi

Nuclear Medicine PhysicianNuclear Medicine Physician

Aga Khan University Hospital, NairobiAga Khan University Hospital, Nairobi

TreatmentTreatment

Antithyroid medicationsAntithyroid medications Iodine-131 therapyIodine-131 therapy SurgerySurgery

Antithyroid medicationsAntithyroid medications

Thionamides. All inhibit the function of Thionamides. All inhibit the function of TPOTPO, reducing oxidation and organification , reducing oxidation and organification of iodide. of iodide.

Propylthiouracil inhibits deiodination of T4 Propylthiouracil inhibits deiodination of T4 to T3. to T3.

Antithyroid medicationsAntithyroid medications

Maximum remission rates are achieved by Maximum remission rates are achieved by 18 to 24 months.18 to 24 months.

The common side effects of antithyroid The common side effects of antithyroid drugs are rash, urticaria, fever, and drugs are rash, urticaria, fever, and arthralgia (1 to 5% of patients).arthralgia (1 to 5% of patients).

Rare but major side effects include Rare but major side effects include hepatitis, an hepatitis, an SLESLE-like syndrome, and, most -like syndrome, and, most importantly, agranulocytosis (<1%).importantly, agranulocytosis (<1%).

Relapse rate is over 50%.Relapse rate is over 50%.

SurgerySurgery

Subtotal thyroidectomy is an option for Subtotal thyroidectomy is an option for patients who relapse after antithyroid drugs patients who relapse after antithyroid drugs and prefer this treatment to radioiodine.and prefer this treatment to radioiodine.

Large goitre.Large goitre. Complications - hypoparathyroidism, and Complications - hypoparathyroidism, and

damage to the recurrent laryngeal nerves damage to the recurrent laryngeal nerves Recurrence rates Recurrence rates Hypothyroidism is only slightly less than Hypothyroidism is only slightly less than

that following radioiodine treatment.that following radioiodine treatment.

Iodine-131 therapyIodine-131 therapy

First patient treated with radioiodine First patient treated with radioiodine (Iodine-130) in 1941.(Iodine-130) in 1941.

Iodine-131 was introduced in 1946.Iodine-131 was introduced in 1946. Iodine-131Iodine-131

Beta particle emissionsBeta particle emissions

Range in tissue --- 0.8 mmRange in tissue --- 0.8 mm

IndicationsIndications

Any patients above a preselected age limitAny patients above a preselected age limit Patients who fail to respond to anti-thyroid Patients who fail to respond to anti-thyroid

drugsdrugs Prior thyroid or other neck surgeryPrior thyroid or other neck surgery Contraindications to surgery such as severe Contraindications to surgery such as severe

heart, lung or renal diseaseheart, lung or renal disease

ContraindicationsContraindications

Pregnancy Pregnancy LactationLactation Question of malignant thyroid tumourQuestion of malignant thyroid tumour Age belowAge below a preselected age limit such as a preselected age limit such as

(possibly) age 15-18(possibly) age 15-18 Patient concerns regarding radiation exposurePatient concerns regarding radiation exposure Severe thyrotoxicosis --- pretreat with antithyroid Severe thyrotoxicosis --- pretreat with antithyroid

medications and beta blockersmedications and beta blockers Severe ophthalmopathySevere ophthalmopathy

Iodine-131 therapyIodine-131 therapy

Thyroid scan with radioiodine uptake, or Thyroid scan with radioiodine uptake, or technetium scan.technetium scan.

Calculation of the Iodine-131 dose.Calculation of the Iodine-131 dose. Pretreatment with antithyroid drugs.Pretreatment with antithyroid drugs. Stopping antithyroid drugs before therapy.Stopping antithyroid drugs before therapy. Ingestion of Iodine-131.Ingestion of Iodine-131. Radiation precautions.Radiation precautions.

ProcedureProcedure

Thyroid ScanThyroid Scan Dose determinationDose determination Calculated dose --- 80-200 Calculated dose --- 80-200 µCi/gmµCi/gm Fixed doseFixed dose Higher doses for solitary toxic nodule and Higher doses for solitary toxic nodule and toxic multi-nodular goitretoxic multi-nodular goitre TherapyTherapy PreparationPreparation PrecautionsPrecautions No significant effect till 2-3 weeksNo significant effect till 2-3 weeks Maximum effect by 3-4 monthsMaximum effect by 3-4 months

Factors Affecting TreatmentFactors Affecting Treatment

Iodine uptakeIodine uptake Size of goitreSize of goitre Length of time I-131 is retained in the glandLength of time I-131 is retained in the gland Homogeneity of distribution within the glandHomogeneity of distribution within the gland Radiosensitivity of thyroid cellsRadiosensitivity of thyroid cells Drug interactionsDrug interactions Antithyroid medicationsAntithyroid medications

Thyroid hormonesThyroid hormones Topical IodineTopical Iodine Radiographic contrast agentsRadiographic contrast agents AmiodaroneAmiodarone

Side EffectsSide Effects

Transient sore throat or mild dysphagiaTransient sore throat or mild dysphagia Exacerbation of ophthalmopathyExacerbation of ophthalmopathy Radiation thyroiditisRadiation thyroiditis No increase in incidence of No increase in incidence of Thyroid cancerThyroid cancer Leukemia or other malignanciesLeukemia or other malignancies No harmful effect uponNo harmful effect upon Health of progenyHealth of progeny FertilityFertility Reproductive historyReproductive history

Empirical dual dose therapyEmpirical dual dose therapy

15 and 20 mCi15 and 20 mCi Number of patients --- 126Number of patients --- 126 Follow-up --- 5 yearsFollow-up --- 5 years OutcomeOutcome

Hypothyroid --- 85.5%Hypothyroid --- 85.5%

Euthyroid --- 7.5%Euthyroid --- 7.5%

No response --- 8%No response --- 8%

ConclusionConclusion

Radioiodine therapy for hyperthyroidismRadioiodine therapy for hyperthyroidism EffectiveEffective SimpleSimple SafeSafe CheapCheap Treatment of choiceTreatment of choice Patients above 30Patients above 30 Patients with medical complicationsPatients with medical complications Relapse after medical therapyRelapse after medical therapy Recurrence after surgeryRecurrence after surgery