By which mechanism, does medullary thyroid cancer cause secretory diarrhea?
Medullary thyroid carcinoma is usually associated with men syndrome in which we get VIPoma, which is associated with diarrhoea.
Upto date: "Systemic symptoms may occur due to hormonal secretion by the tumor. Tumor secretion of calcitonin, calcitonin-gene related peptide, or other substances can cause diarrhea or facial flushing in patients with advanced disease. In addition, occasional tumors secrete corticotropin (ACTH), causing ectopic Cushing's syndrome."
Colonic function was markedly impaired in three ways: (a) water absorption was decreased by half; (b) as the main excreted solutes were organic acids, a large electrolyte gap was recorded in faecal water, and (c) colonic transit time of the meal marker was very short, and was in agreement with the rapid transit of ingested radioopaque markers. These data strongly suggest that decreased absorption in the colon secondary to a motor disturbance is the main mechanism of diarrhoea in this case of medullary thyroid carcinoma, while calcitonin induced small intestinal fluid secretion suggested earlier is either non-existent, or only of minor importance.
My dd for tumors and secretory diarrhea (someone wants to add):
- carcinoid tumor
- Medullary thyroid cancer