Conclusion:
Medullary thyroid cancer can present with various symptoms. Diarrhea is a rare symptom of MTC which, when present, could be due to increased secretion of calcitonin and other active peptides by tumor cells [21]. Our patient presented with diarrhea as the primary chief complaint prompting extensive workup, which was negative. It is important for providers to have malignancies like MTC at the back of their minds while evaluating patients with chronic diarrhea. Early diagnosis of MTC can lead to more effective individualized treatments.