I have had diarrhea for about seven months. After many tests, the only thing unusual is a high level of some hormone from the stomach in my blood. I have never heard of a "stomach hormone." Can you provide details?

V.K.

Diarrhea is a common problem that often leads people to consult gastroenterologists. Possible causes of chronic diarrhea include infections, inflammation in the small intestine or colon, side effects of medication, pancreatic dysfunction, endocrine disorders and tumors.

You mention a "stomach hormone," and I assume you are referring to gastrin. Gastrin is a hormone that is normally released from the stomach in response to a meal. Its function is to regulate the production of acid from the stomach, an important part of digestion.

There is a condition, known as Zollinger-Ellison syndrome (or gastrinoma), in which a tumor produces excessively large amounts of gastrin. The tumor is usually located in the pancreas or duodenum, and because it can be very small, it may be hard to locate on imaging examinations. The excess gastrin leads to excess acid production by the stomach. Patients often suffer from severe ulcer disease in the stomach and duodenum that may not respond to the usualanti-acid therapies. In addition, diarrhea is a common component of gastrinoma. The reasons for the diarrhea are several: First, the excess acid from the stomach leads to increased fluid in the intestine, which then passes down into the colon. Also, the acid in the intestine disables the normal bile acids and pancreatic enzymes necessary for normal digestion. The result is soft or liquid stool with large amounts of undigested fat in it.

Although you may have an elevated gastrin level in your blood, other factors besides a gastrinoma may cause this abnormal reading. These include certain medications, kidney disease and the timing of a meal relative to when your blood was drawn. If your doctor suspects a gastrinoma, he will want to perform certain imaging tests to localize the tumor. The treatment options will depend on those findings and may include medications to prevent acid production and/or surgery for the tumor. You should discuss your concerns with your doctor.