In a patient with Graves disease on methimazole who has a suspicious thyroid nodule and is planning thyroidectomy, should methimazole be continued up to the day of surgery?

Continue Methimazole Until Day of Surgery

Yes, continue methimazole up to and including the day of surgery, then stop it at the time of thyroidectomy. 1

Preoperative Management Algorithm

The American Thyroid Association/American Association of Clinical Endocrinologists guidelines are explicit and unequivocal on this point:

Patients with Graves' disease undergoing thyroidectomy should be rendered euthyroid with methimazole whenever possible. 1 This is a Level 1 recommendation, meaning it carries the strongest evidence grade.

Step-by-Step Approach:

1. Continue methimazole at the current dose that maintains euthyroid status

   • Do not taper or discontinue preoperatively
   • The goal is to prevent thyroid storm, which can be precipitated by surgical stress, anesthesia, or thyroid manipulation 1

2. Add potassium iodide in the immediate preoperative period 1

   • Give 5-7 drops (0.25-0.35 mL) Lugol's solution (8 mg iodide/drop) OR
   • Give 1-2 drops (0.05-0.1 mL) SSKI (50 mg iodide/drop)
   • Administer three times daily for 10 days before surgery
   • This decreases thyroid vascularity and intraoperative blood loss 1

3. Stop methimazole on the day of surgery 1

   • Antithyroid drugs should be discontinued at the time of thyroidectomy
   • Beta-blockers (if used) should be weaned postoperatively

Critical Safety Considerations

Why This Matters for Morbidity and Mortality:

• Thyroid storm prevention: Operating on a hyperthyroid patient significantly increases the risk of life-threatening thyroid storm 1
• Surgical complications: Uncontrolled hyperthyroidism increases thyroid vascularity, leading to greater intraoperative bleeding 1
• Cardiovascular risk: Hyperthyroid patients have increased risk of perioperative arrhythmias and cardiovascular complications

The Suspicious Nodule Does Not Change This Approach:

The guidelines specifically address this scenario: "If a thyroid nodule is discovered in a patient with GD, the nodule should be evaluated and managed according to recently published guidelines regarding thyroid nodules in euthyroid individuals." 1

The key word is "euthyroid" - you still need to achieve euthyroid status before surgery, regardless of the nodule. The presence of a suspicious nodule is actually an indication for surgery rather than radioactive iodine, but it doesn't change the preoperative preparation protocol.

Exception (Rare):

Only in exceptional circumstances when it's impossible to render the patient euthyroid, the surgery is urgent, or the patient is allergic to antithyroid medication, should you proceed differently. In these cases, use beta-blockade plus potassium iodide, and ensure the surgeon and anesthesiologist have experience managing this high-risk situation. 1

Postoperative Management:

• Start levothyroxine at 0.8 μg/lb (1.7 μg/kg) daily 1
• Check serum calcium or intact PTH levels 1
• Monitor TSH at 6-8 weeks postoperatively 1