Persistent Duodenal Ulcers: Order a Serum Gastrin Next

A 38-year-old woman presents with hematemesis. Upper endoscopy reveals a duodenal ulcer with an actively spurting vessel. Hemostasis is achieved with injection of epinephrine followed by thermal coagulation. She also has several other non-bleeding shallow ulcers in other portions of the duodenum. Biopsies are negative for Helicobacter pylori. This has been her third presentation of an upper GI bleed secondary to duodenal ulcers in the past 2 years. On review of systems, she complains of intermittent diarrhea and has unintentionally lost 5 lb over the past month. Which of the following should be ordered next?

A. Serum glucagon
B. Serum prolactin
C. Serum gastrin
D. 24-hour urinary 5HIAA

Answer: C

This is a presentation of a gastrinoma, or Zollinger-Ellison syndrome, a type of neuroendocrine tumor that may be associated with multiple endocrine neoplasia type I. 

Gastrinomas secrete excess amounts of gastrin, a peptide hormone that stimulates the secretion of hydrochloric acid from parietal cells. As a result, multiple ulcers can occur in the stomach and duodenum. In addition, patients with this condition may complain of diarrhea and weight loss. A serum gastrin level should be checked and will likely exceed 1000 pg/mL (upper limit of normal, 100 pg/mL).

Glucagonoma is a rare pancreatic neuroendocrine tumor, which may present with markedly elevated levels of serum glucagon. However, mild elevations are not specific and may occur in fasting states, in the setting of trauma or surgery, or with renal and hepatic failure. The clinical manifestations include diabetes; diarrhea; weight loss; and a rash that may precede symptoms, called necrolytic migratory erythema. Ulcers do not occur as part of this clinical syndrome. Hyperprolactemia can cause hypogonadism, galactorrhea, and infertility, but not duodenal ulcers. Finally, measuring 24-hour urinary 5HIAA, which is the end product of serotonin metabolism, would screen for carcinoid. This is a neuroendocrine tumor that can be localized to the upper GI tract, including the duodenum. Symptoms can include diarrhea and weight loss, but not ulcers.