Should Thyronorm (levothyroxine) be administered on the day of surgery?

Perioperative Management of Levothyroxine (Thyronorm) on Surgery Day

Levothyroxine (Thyronorm) should be administered on the day of surgery without interruption. 1

Rationale for Continuing Levothyroxine

Levothyroxine is essential for maintaining thyroid hormone levels, which are critical for:

• Maintaining metabolic function during surgery
• Preventing hypothyroid complications in the perioperative period
• Ensuring TSH levels remain appropriately controlled for thyroid cancer patients

Evidence-Based Recommendations

Current perioperative guidelines from the American Diabetes Association specifically address thyroid hormone medication management:

• While many oral medications should be held on the day of surgery, levothyroxine is an exception 1
• Unlike medications such as metformin (which should be held on surgery day) or SGLT2 inhibitors (which should be discontinued 3-4 days before surgery), thyroid hormone replacement should be continued 1

Clinical Considerations

For Thyroid Cancer Patients

For patients with thyroid cancer on suppressive levothyroxine therapy:

• Maintaining appropriate TSH suppression is critical for preventing cancer recurrence 2
• Target TSH levels vary based on risk stratification:
  • High-risk patients: TSH <0.1 mIU/L
  • Intermediate-risk patients: TSH 0.1-0.5 mIU/L
  • Low-risk patients: TSH 0.5-2.0 mIU/L 2
• Interruption of therapy can lead to TSH elevation, potentially stimulating residual thyroid cancer cells

For Hypothyroid Patients

For patients on replacement therapy for hypothyroidism:

• Untreated hypothyroidism increases surgical risks, including:
  • Intraoperative hypotension (61% vs 30% in euthyroid patients)
  • Increased risk of gastrointestinal complications (19% vs 1%)
  • Higher rates of neuropsychiatric complications (38% vs 18%) 3
• Maintaining euthyroid status is essential for optimal surgical outcomes

Practical Administration Guidelines

1. Timing: Administer levothyroxine early on the morning of surgery with a small sip of water
2. Dosing: Give the patient's regular dose unless otherwise specified
3. Documentation: Ensure the medication is listed as a "take on day of surgery" medication in preoperative orders
4. Monitoring: Check thyroid function tests postoperatively if the patient will have prolonged NPO status

Special Circumstances

Extended NPO Status

If a patient will be NPO for an extended period postoperatively:

• Consider alternative administration routes (IV levothyroxine) if NPO status will exceed 5-7 days
• Monitor thyroid function tests if extended NPO status is anticipated

Emergent Surgery

For emergent surgery in patients with unknown thyroid status:

• Proceed with surgery
• Obtain baseline thyroid function tests
• Initiate appropriate thyroid replacement postoperatively if hypothyroidism is identified

Conclusion

The evidence strongly supports continuing levothyroxine (Thyronorm) on the day of surgery. The risks of interrupting therapy (rising TSH levels, potential hypothyroid complications) outweigh any theoretical concerns about medication administration on the day of surgery.