Hyperthyroidism Treatment
Pharmacotherapy
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
Surgical Intervention
- 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
Radiotherapy
- 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
Ophthalmopathy
- 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