Should levothyroxine (thyroid hormone replacement medication) be held before surgery?

Management of Levothyroxine Before Surgery

Levothyroxine should be continued and administered on the morning of surgery. 1

Rationale for Continuing Levothyroxine

• Levothyroxine is a thyroid hormone replacement medication that should be maintained at consistent levels to avoid fluctuations in thyroid hormone status 1
• Postoperative levothyroxine is indicated for all thyroidectomy patients, with TSH kept in the normal range through appropriate dosing 1
• Unlike medications that may increase bleeding risk or interfere with anesthesia, levothyroxine does not need to be held before surgery 1
• Abrupt discontinuation of levothyroxine can lead to hypothyroidism, which is associated with increased perioperative complications 2

Risks of Withholding Levothyroxine

• Hypothyroidism has been associated with increased risk of intraoperative hypotension during noncardiac surgery (61% vs 30% in euthyroid patients) 2
• Hypothyroid patients undergoing cardiac surgery have higher rates of heart failure complications (29% vs 6%) 2
• Postoperative gastrointestinal (19% vs 1%) and neuropsychiatric (38% vs 18%) complications are more common in hypothyroid patients 2
• Hypothyroid patients may have impaired fever response to infection, making detection of postoperative infections more difficult 2

Special Considerations

Thyroid Cancer Patients

• For patients with differentiated thyroid cancer, TSH suppression therapy is an important part of treatment 1
• In high-risk thyroid cancer patients, maintaining TSH suppression may decrease progression of metastatic disease 1
• Interrupting levothyroxine therapy could lead to rising TSH levels, which is undesirable in thyroid cancer management 1

Medullary Thyroid Carcinoma Patients

• For patients with medullary thyroid carcinoma (MTC), TSH suppression is not appropriate since C cells lack TSH receptors 1
• However, these patients still require levothyroxine replacement to maintain normal thyroid function 1
• TSH should be kept in the normal range through appropriate levothyroxine dosing 1

Postoperative Management

• After thyroidectomy, achieving euthyroidism can take nearly 4 months 3
• Patients typically require at least one dose adjustment before achieving stable thyroid hormone levels 3
• Thyroid function tests should be checked approximately 6 weeks after surgery to assess adequacy of levothyroxine dosing 4
• Patients taking iron supplements or multivitamins with minerals may require more dose adjustments to achieve euthyroidism 3

Conclusion

Levothyroxine should be continued up to and including the day of surgery. The risks of withholding levothyroxine (potential hypothyroidism and associated complications) outweigh any theoretical benefits of discontinuation. Maintaining consistent thyroid hormone levels is important for optimal perioperative outcomes.