Pembrolizumab & Hypothyroidism: A Common Endocrine Side Effect in Oncocrinology
Timeline: Hypothyroidism frequently develops within the first 3 months of initiating pembrolizumab, a PD-1 immune checkpoint inhibitor widely used in cancer therapy.
Pathophysiology: The drug enhances T-cell activity against tumors, but this immune activation can also target the thyroid gland, resulting in immune-mediated thyroiditis and subsequent hypothyroidism.
Clinical symptoms to monitor:
- Persistent fatigue
- Unexplained weight gain
- Cold intolerance
- Constipation
- Depressive symptoms
Recommended monitoring: Assess TSH and free T4 levels every 6 to 12 weeks during immunotherapy.
Management: Most patients require levothyroxine replacement therapy. Importantly, pembrolizumab can typically be continued with appropriate endocrine management.
Clinical insight: Prompt recognition and treatment of thyroid dysfunction can significantly improve quality of life and ensure uninterrupted cancer care.
