Glucagon is a hormone secreted by the alpha cells of the islets of Langerhans in the pancreas in response to hypoglycemia. This hormone acts primarily on the liver to promote glucose production from glycogen stores and to control glycogen storage. Glucagon also produces glucose from the oxidation of fatty acids like triglycerides to basic glycerol components. The coordinated release of insulin, glucagon, and somatostatin ensures an adequate fuel supply while maintaining stable blood glucose. Patients with glucagonoma have values greater than 500 ng/L. Values greater than 1,000 ng/L are diagnostic for this condition. Glucagonoma causes three different syndromes:

• Syndrome 1: A characteristic skin rash, diabetes or impaired glucose tolerance, weight loss, anemia, and venous thrombosis
• Syndrome 2: Severe diabetes
• Syndrome 3: Multiple endocrine neoplasia

A dramatic increase in glucagon occurring soon after renal transplant may indicate organ rejection. In the case of kidney transplant rejection, glucagon levels increase several days before an increase in creatinine levels.

Glucagon deficiency can be confirmed by measuring glucagon levels before and after IV infusion of arginine 0.5 g/kg. Glucagon deficiency is confirmed when levels fail to rise 30 to 60 min after infusion. Newborn infants of diabetic mothers have impaired glucagon secretion, which may play a role in their hypoglycemia.