Type of test

 Blood

Normal findings

 50-100 pg/mL or 50-100 ng/L (SI units)

Test explanation and related physiology

Glucagon is a hormone secreted by the alpha cells of the pancreatic islets of Langerhans. It is secreted in response to hypoglycemia and increases the blood glucose. As serum glucose levels rise in the blood, glucagon is inhibited by a negative feedback mechanism.

Elevated glucagon levels may indicate the diagnosis of a glucagonoma (i.e., an alpha islet cell neoplasm). Glucagon deficiency occurs with extensive pancreatic resection or with burned-out pancreatitis. Arginine is a potent stimulator of glucagon. If glucagon levels fail to rise even with arginine infusion, a diagnosis of glucagon deficiency as a result of pancreatic insufficiency is confirmed.

In an insulin-dependent patient with diabetes, glucagon stimulation caused by hypoglycemia does not occur. To differentiate the causes of glucagon insufficiency between pancreatic insufficiency and diabetes, arginine stimulation is performed. Patients with diabetes will have an exaggerated elevation of glucagon with arginine. In pancreatic insufficiency, glucagon is not stimulated with argi nine. Furthermore, in patients with diabetes, hypoglycemia fails to stimulate glucagon release as would occur in a nondiabetic person.

Because glucagon is thought to be metabolized by the kidneys, renal failure is associated with high glucagon and, as a result, high glucose levels. When rejection of a transplanted kidney occurs, one of the first signs of rejection may be increased serum glucagon levels.

Interfering factors

 • Levels may be elevated after prolonged fasting or moderate to severe exercise.

* Drugs that may cause increased levels include some amino acids (e.g., arginine), danazol, gastrin, glucocorticoids, insulin, and nifedipine.

* Drugs that may cause decreased levels include atenolol, propranolol, and secretin.

Procedure and patient care

• See inside front cover for Routine Blood Testing.

 • Fasting: yes

 • Blood tube commonly used: lavender

Abnormal findings

Increased levels

- Familial hyperglucagonemia

 - Glucagonoma

 - Diabetes mellitus

 - Chronic renal failure

 - Severe stress including infection, burns, surgery, and acute hypoglycemia

 - Acromegaly

 - Hyperlipidemia

 - Acute pancreatitis

 - Pheochromocytoma

Decreased levels

- Idiopathic glucagon deficiency

- Cystic fibrosis

 - Chronic pancreatitis

 - Postpancreatectomy

- Cancer of the pancreas

 - Diabetes mellitus