Patient was admitted. Physical exam revealed a benign abdomen, but was notable for multiple thyroid nodules. Workup commenced with repeat infectious stools studies including Clostridium difficile PCR, which were negative. Thereafter, she was placed on loperamide with improvement in her stool frequency. A hormonal cause of her diarrhea was considered and serum levels of serotonin, vasoactive intestinal peptide, pancreatic polypeptide, neurotensin, pancreastatin, gastrin, calcitonin, glucagon, chromogranin A, substance P and TSH were sent. In the interim, CT abdomen/pelvis was checked and revealed numerous liver lesions of unclear etiology, and were confirmed by MRI liver. The largest lesion, measuring 4.7 x 4.3 cm, was biopsied. Subsequently, patient’s serum calcitonin level resulted at 222,457 pg/mL (ref range <5 pg/mL). Liver pathology revealed a well-differentiated neuroendocrine tumor with cells staining positive for calcitonin. Both of these findings, in the setting of thyroid nodules, were suggestive of metastatic medullary thyroid cancer.
Patient was discharged home after outpatient thyroid nodule biopsy was scheduled. It confirmed the diagnosis of medullary thyroid cancer. She subsequently underwent transarterial chemoembolization (TACE) of the left hepatic artery. Future plans are for TACE of the right hepatic artery and then intervention on her thyroid, which will likely be a total thyroidectomy.
Discussion: This patient’s diarrhea was typical of secretory diarrhea; profuse watery stools unaffected by meals. Extensive outpatient and inpatient workup was unrevealing until hormone levels and cross-sectional imaging were performed. These studies appropriately came later in the workup, after more common etiologies including inflammatory and malabsorptive diarrhea, were ruled out.
Conclusions: Hormonal causes of diarrhea are rare but important. Calcitonin is known to cause diffuse watery diarrhea as well as flushing, similar to the classic manifestations of carcinoid syndrome. An elevated calcitonin level is most frequently associated with medullary thyroid cancer. Medullary thyroid cancer can be sporadic or inherited as part of the MEN 2A/B syndromes. In about 1/3 of patients with medullary thyroid cancer, diarrhea is the initial presenting symptom.