Hyperthyroidism Treatment

Antithyroid Agents

• Carbimazole & Methimazole are considered 1st-line treatment
• 2 methods in treating hyperthyroid patients
  
  • Dose titration: Dose is reduced & titrated against thyroid function tests to achieve a euthyroid state
  • Block & replace regimen: Combination therapy with thyroid preparation (eg Levothyroxine) may be considered in patients inadequately controlled by single-dose Carbimazole or Methimazole therapy, or in noncompliant patients 
• Effects: About 25% of patients remain euthyroid ≥5 years after antithyroid treatment
  
  • Remission is most likely to occur in patients with a small thyroid gland (<2.5x normal size for age), children & adolescents >13 years old, non-Caucasian, serum TRAb levels less than normal or low T4 levels during therapy
  • Relapse usually appears within 3-6 months after stopping the therapy
• Usually takes 3-6 weeks for clinical response to be noticeable
  
  • 3-4 months to have adequate control
  • May use beta-blockers to control symptoms during this period, but not always needed

Carbimazole

• Inhibit thyroid hormone biosynthesis by decreasing iodide oxidation & iodination of tyrosine
• Recommended as first-line antithyroid treatment in pediatric patients
• Fewer tablets are needed for initial treatment compared w/ Propylthiouracil (PTU)

Methimazole

• Methimazole is preferred over PTU because of less adverse effects 
  • 10-fold more potent on wt basis than PTU
• Recommended as first-line antithyroid treatment in pediatric patients

Propylthiouracil (PTU)

• Blocks the conversion of T₄ to T₃ in thyroid gland & peripheral tissues, also inhibits thyroid hormone biosynthesis by decreasing iodide oxidation & iodination of tyrosine
• May be considered in patients with minimal response to Carbimazole or Methimazole therapy & opposed to surgical or radioactive iodine treatment, or patients with thyroid storm
• Patients/caregivers should be informed of the potential to develop irreversible hepatic dysfunction with long-term
• PTU therapy
  • Obtaining a written consent prior to initiation of PTU therapy is advised

Symptomatic Management
Beta-Blockers

• Eg Propanolol, Atenolol, Metoprolol, Nadolol
• Recommended for symptomatic treatment of hyperthyroidism especially in children with a heart rate (HR) of >100 bpm
• Contraindicated in hyperthyroidism patients w/ bronchospastic asthma
  
  • Nadolol may be given to asthmatic hyperthyroidism patients w/ mild chronic obstructive pulmonary disease (COPD), symptomatic Raynaud’s phenomenon, or those whom HR control is essential
• Atenolol is the most used beta-blocker because of its cardioselective property, thus less risk for bronchospasm
• Esmolol is preferred over other beta-blockers for older intensive care unit (ICU) patients w/ thyroid storm/severe thyrotoxicosis

• Patients may undergo near-total or total thyroidectomy
• Effects: Up to 97% cure rate when performed by experienced surgeons
• Indications:
  
  • Sufficient cooperation for medical therapy is not possible
  • Adequate trial of antithyroid agents has failed to cause permanent remission
  • Intolerance to severe side effects of antithyroid drugs
  • Large thyroid gland size (>80 g)
  • Need for immediate disease control
  • <5 years of age
  • For very young patients intolerant to radioactive iodine therapy
• Potential complications: Hypoparathyroidism, recurrent laryngeal nerve paralysis, hemorrhage, hypocalcemia
• Iodine therapy rather than surgery is more advisable for patients with thyroid enlargement of >80 g

Prior to Surgery

• Restoration of euthyroidism
  
  • Antithyroid drug treatment over 1-2 months prior to surgery
  • Iodide (eg saturated solution of potassium iodide) is added in the regimen x 10 days prior to surgery; given to decrease the vascularity of the thyroid gland

Permanent Hypothyroidism

• If patient becomes hypothyroid, T₄ replacement may be considered

• Effective & relatively safe in patients >10 years
  
  • May be considered in patients 5-10 years old but caution during duration of therapy is recommended
• Main goal is to induce hypothyroidism; may be considered in patients who relapse after medical therapy
• A single therapeutic dose of RAI 200-300 μCi/g of thyroid tissue is recommended
• Consider pretreatment with β-adrenergic blockade & antithyroid agents in asymptomatic patients with Graves’disease at increased risk for complications caused by exacerbation or worsening of hyperthyroidism
• Patients may expect long-term thyroid replacement with thyroxine (T₄)
• Frequency of radioactive iodine therapy is reduced due to theoretical risk of malignancy or genetic damage
• Instructions on radiation safety precautions immediately following treatment
  
  • Close & prolonged physical contact with other people should be avoided for 3 days
  • Caregiver is advised to have the patient take a break from daycare or school for 2 weeks

• Usually resolves gradually & independently of hyperthyroidism
  
  • May resolve when patient becomes euthyroid
• Some symptoms may not resolve especially if the symptoms are caused by autoimmune reaction against fibroblasts or muscles of the orbit
• May be treated w/ high-dose Prednisone
• Surgical decompression of orbits or orbital radiotherapy may also be done