What is the diagnosis and treatment for a patient with hyperthyroidism?

Overt Hyperthyroidism: Suppressed TSH with Elevated Free T4

This patient has overt hyperthyroidism requiring immediate treatment to prevent serious cardiovascular, bone, and metabolic complications. With a TSH of 0.01 mIU/L (suppressed) and free T4 of 1.49 ng/dL (elevated above normal range of approximately 0.8-1.8 ng/dL), this represents autonomous thyroid hormone overproduction that demands urgent intervention 1.

Immediate Diagnostic Workup

Establish the underlying etiology before initiating treatment, as this determines your therapeutic approach:

• Measure TSH-receptor antibodies (TRAb) to diagnose Graves' disease, which accounts for 70% of hyperthyroidism cases 2, 1
• Obtain thyroid ultrasound to identify toxic nodular goiter (16% of cases) or assess for thyroiditis 2
• Order thyroid scintigraphy if nodules are present or etiology remains unclear after initial testing 1
• Check thyroid peroxidase antibodies (TPO) to help differentiate autoimmune causes 2

Critical pitfall: Do not delay treatment while awaiting antibody results if the patient has severe symptoms, cardiac complications, or signs of thyroid storm 3.

Treatment Algorithm Based on Etiology

For Graves' Disease (Most Likely Diagnosis)

Initiate antithyroid drug therapy immediately as first-line treatment:

• Methimazole is the preferred antithyroid drug for most patients, as it inhibits thyroid hormone synthesis 4, 5, 6
• Standard initial dose: 10-30 mg daily depending on severity of hyperthyroidism 5, 6
• Continue for 12-18 months to induce remission, though recurrence occurs in approximately 50% of patients 2

Consider definitive therapy with radioactive iodine (RAI) or surgery if:

• Patient has contraindications to antithyroid drugs 5, 6
• Recurrence occurs after completing antithyroid drug course 2
• Patient preference for definitive cure 5, 1
• Large goiter causing compressive symptoms 6

RAI ablation is the most widely used treatment in the United States and offers definitive cure, though hypothyroidism is the expected long-term outcome 5, 6.

For Toxic Nodular Goiter

Radioactive iodine is the treatment of choice for toxic nodular goiter, as antithyroid drugs will not cure this condition 6, 2.

Alternative options include:

• Thyroidectomy for large goiters causing compressive symptoms 6
• Radiofrequency ablation in select cases 2

For Thyroiditis (Destructive Thyrotoxicosis)

Observation with supportive care is appropriate if thyroiditis is confirmed, as this condition is usually mild and transient 2, 1.

Steroids are reserved for severe cases only 2.

Critical Monitoring During Treatment

Monitor thyroid function tests periodically during antithyroid drug therapy:

• Once clinical hyperthyroidism resolves, a rising TSH indicates the need for dose reduction to prevent iatrogenic hypothyroidism 4
• Check complete blood count if patient develops fever, sore throat, or malaise to detect agranulocytosis, a serious adverse effect of methimazole 4
• Monitor prothrombin time before surgical procedures as methimazole may cause hypoprothrombinemia 4

Special Populations Requiring Modified Approach

Pregnancy Considerations

Methimazole carries risk of congenital malformations in the first trimester:

• Consider propylthiouracil (PTU) for first trimester despite its hepatotoxicity risk 4
• Switch to methimazole for second and third trimesters to minimize maternal hepatotoxicity 4
• Avoid pregnancy for 4 months after radioactive iodine administration 6
• Untreated Graves' disease increases risk of maternal heart failure, spontaneous abortion, preterm birth, and fetal hyperthyroidism 4

Patients with Cardiac Disease or Atrial Fibrillation

Untreated hyperthyroidism causes cardiac arrhythmias and heart failure:

• Initiate beta-blockers immediately to control heart rate and reduce cardiac workload 7
• Hyperthyroidism increases clearance of beta-blockers, requiring higher doses initially 4
• Dose reduction of beta-blockers will be needed once patient becomes euthyroid 4

Elderly Patients

Older adults (>60 years) with hyperthyroidism have 3-fold increased risk of atrial fibrillation over 10 years 7.

Treatment is particularly urgent in this population to prevent cardiovascular mortality 1.

Risks of Untreated Hyperthyroidism

Delaying treatment carries serious consequences:

• Cardiac arrhythmias and heart failure from increased cardiac output and decreased systemic vascular resistance 7, 1
• Osteoporosis and fracture risk from accelerated bone turnover 8, 1
• Unintentional weight loss and metabolic derangements 1
• Increased all-cause mortality if hyperthyroidism remains uncontrolled 2, 1
• Adverse pregnancy outcomes including preeclampsia and low birth weight 4

Common Pitfalls to Avoid

Do not confuse subclinical hyperthyroidism (low TSH with normal T4/T3) with overt hyperthyroidism - this patient has overt disease requiring immediate treatment 1.

Do not assume a single etiology - obtain definitive testing with antibodies and imaging to guide treatment selection 2, 1.

Do not use radioactive iodine in pregnancy, lactation, or within 4 months of planned conception 6.

Do not overlook drug interactions - adjust doses of warfarin, digoxin, theophylline, and beta-blockers as patient becomes euthyroid 4.

Monitor for agranulocytosis - instruct patients on methimazole to report fever, sore throat, or malaise immediately 4.