What are the initial management options for hyperthyroidism?

Management of Hyperthyroidism

Initial Diagnostic Approach

For symptomatic patients with suspected hyperthyroidism, check TSH and free T4 first, then add T3 levels in highly symptomatic patients with minimal FT4 elevations to confirm biochemical hyperthyroidism 1.

• Obtain TSH-receptor antibodies to diagnose Graves' disease, as this distinguishes autoimmune hyperthyroidism from other causes 1.
• Physical examination must assess for diffuse goiter, thyroid bruit, or ophthalmopathy—these findings are diagnostic of Graves' disease and warrant early endocrine referral 2, 1.
• Consider ultrasound and radioactive iodine uptake scan to differentiate between Graves' disease, toxic multinodular goiter, and toxic adenoma 3.

First-Line Pharmacologic Treatment

Methimazole is the preferred antithyroid drug for most patients due to once-daily dosing, fewer severe side effects, and lower cost 1, 4, 5.

Methimazole Dosing

• Start with 10-30 mg daily as a single dose for mild to moderate hyperthyroidism without large goiter 6.
• For severe hyperthyroidism or large goiter, initiate 30-40 mg daily 6.
• Maintenance doses are typically 5-10 mg daily 6.
• Monitor free T4 or free thyroxine index every 2-4 weeks initially, adjusting dosing to maintain FT4 in the high-normal range using the lowest possible dose 1.
• Once stable, check TSH and free T4 after 6-8 weeks 1.

Propylthiouracil Use

• Propylthiouracil is reserved specifically for the first trimester of pregnancy due to methimazole's association with aplasia cutis and choanal/esophageal atresia 1, 7.
• Starting dose is 100-300 mg every 6 hours 6.
• Consider switching to methimazole for the second and third trimesters given propylthiouracil's hepatotoxicity risk 4, 8.
• PTU should be restricted to first trimester at doses of 150-200 mg/day 6.

Symptomatic Management

Start beta-blocker therapy immediately to control cardiovascular symptoms while waiting for antithyroid drugs to take effect 1, 3.

• Atenolol 25-50 mg daily or propranolol are appropriate first-line choices 2, 1.
• Titrate to heart rate <90 bpm if blood pressure allows 1.
• Beta-blockers are particularly critical in elderly patients, as cardiovascular complications are the chief cause of death in older patients with hyperthyroidism 1.
• Continue beta-blockers until the patient becomes euthyroid, then taper as thyroid hormone levels normalize 3.

Critical Safety Monitoring

Patients must be counseled to report immediately any sore throat, fever, skin eruptions, or general malaise—these are warning signs of agranulocytosis 1, 4, 8.

• Obtain white blood cell count with differential if any signs of infection develop 4, 8.
• Monitor for hepatic dysfunction, particularly in the first 6 months: anorexia, pruritus, jaundice, light-colored stools, dark urine, or right upper quadrant pain 8.
• Check liver function tests (bilirubin, alkaline phosphatase, ALT/AST) if hepatic symptoms occur 8.
• Monitor prothrombin time before surgical procedures, as antithyroid drugs may cause hypoprothrombinemia 4, 8.
• Counsel patients to report symptoms of vasculitis: new rash, hematuria, decreased urine output, dyspnea, or hemoptysis 4, 8.

Treatment Duration and Monitoring

Continue antithyroid drug therapy for 12-18 months with a view to inducing long-term remission in Graves' disease 9, 6.

• Monitor thyroid function every 2-3 weeks after diagnosis to catch transition to hypothyroidism, which is the most common outcome for transient thyroiditis 2, 1.
• A rising serum TSH on therapy indicates overtreatment or recovery of thyroid function—reduce or discontinue the dose with close follow-up 2.
• Do not stop antithyroid drugs until TSH-receptor antibodies are within normal range 6.
• For persistent thyrotoxicosis beyond 6 weeks, refer to endocrinology for additional workup 2.

Definitive Treatment Options

Radioactive iodine is increasingly used as first-line definitive therapy and is the treatment of choice for toxic nodular goiter 9, 3.

• Radioiodine is well tolerated with the only long-term sequela being hypothyroidism 9.
• Radioactive iodine is absolutely contraindicated in pregnancy and should be avoided during lactation 1, 9.
• Avoid pregnancy for 4 months following radioiodine administration 9.
• Do not use radioiodine in Graves' disease with ophthalmopathy, as it may cause deterioration—consider corticosteroid cover to reduce this risk 9, 3.

Surgical Indications

• Surgery (total thyroidectomy for Graves' disease and toxic multinodular goiter; lobectomy for toxic adenoma) should be considered for concurrent thyroid cancer, pregnancy, compressive symptoms, or Graves' disease with ophthalmopathy 3.
• Render patients euthyroid with antithyroid medications preoperatively and continue beta-blockers for cardiovascular manifestations 3.

Special Populations

Pregnancy

• Propylthiouracil is the preferred agent during the first trimester of pregnancy 1, 8, 7.
• Switch to methimazole for the second and third trimesters to avoid propylthiouracil's hepatotoxicity 1, 4.
• Use sufficient but not excessive doses to avoid fetal goiter and cretinism 4, 8.
• Thyroid dysfunction often diminishes as pregnancy progresses, allowing dose reduction or discontinuation weeks to months before delivery 4, 8.

Lactation

• Both methimazole and propylthiouracil are present in breast milk in clinically insignificant amounts 4, 8, 6.
• Methimazole/carbimazole can be used during breastfeeding with monitoring of infant thyroid function at weekly or biweekly intervals 4, 6.

Elderly Patients

• Start with lower doses if hypothyroidism develops in elderly patients with cardiovascular disease 1.
• Beta-blockers are essential as cardiovascular complications are more severe in this population 1.
• Hyperthyroidism may increase clearance of beta-blockers, so dose reduction may be needed when the patient becomes euthyroid 4, 8.

Common Pitfalls to Avoid

Do not assume all hyperthyroidism requires antithyroid drugs—thyroiditis-induced thyrotoxicosis is self-limited and typically requires only supportive care with beta-blockers 2, 1.

• Thyroiditis resolves in weeks, most often progressing to primary hypothyroidism or occasionally to normal 2.
• For asymptomatic patients with elevated TSH in the recovery phase of thyroiditis and FT4 in the reference range, monitor for 3-4 weeks before treating to determine if recovery occurs 2.
• Reduce doses of digoxin, theophylline, and beta-blockers as patients become euthyroid, as clearance of these drugs decreases with normalization of thyroid function 4, 8.
• Monitor anticoagulation more closely, as antithyroid drugs may increase warfarin activity through vitamin K inhibition 4, 8.