Unit Converter
Glucagon
(Pancreatic α-Cell Hormone – Key Regulator of Glucose Homeostasis & Counter-Regulatory Response)
Synonyms
- Glucagon
- Pancreatic α-cell hormone
- Hyperglycemic hormone
- Counter-regulatory hormone
- Immunoreactive glucagon (IRG)
Units of Measurement
- ng/L
- ng/dL
- ng/100 mL
- ng%
- pg/mL
Key Conversions
(Molecular weight ≈ 3485 Da)
1 pg/mL = 1 ng/L
1 ng/dL = 10 pg/mL = 10 ng/L
ng/100 mL = ng% = ng/dL
1 ng/L = 1 pg/mL
(Glucagon is measured in mass units, not activity units.)
Description
Glucagon is a 29-amino-acid peptide hormone produced by pancreatic alpha cells.
It is the primary counter-regulatory hormone to insulin, maintaining glucose during fasting by:
- Stimulating hepatic glycogenolysis
- Increasing gluconeogenesis
- Promoting ketogenesis
- Increasing lipolysis
Glucagon secretion rises during:
- Hypoglycemia
- Exercise
- Stress
- Amino-acid ingestion
- Sympathetic activation
Physiological Role
1. Glucose Regulation
Glucagon increases plasma glucose by:
- Breaking glycogen → glucose
- Stimulating hepatic glucose output
- Opposing insulin action
2. Ketone Production
Stimulates ketogenesis during fasting/starvation.
3. Protein Metabolism
Amino-acid ingestion strongly stimulates glucagon.
4. Stress Response
Increases during acute illness, trauma, and exercise.
Clinical Significance
High Glucagon (Hyperglucagonemia)
1. Glucagonoma
Rare α-cell neuroendocrine tumor → excessively high glucagon.
Classic symptoms:
- Necrolytic migratory erythema
- Diabetes / hyperglycemia
- Weight loss
- Anemia
- Diarrhea
Very high glucagon (>500–1000 pg/mL) strongly suggests glucagonoma.
2. Diabetes Mellitus
- Inappropriately elevated fasting & postprandial glucagon
- Contributes to hyperglycemia
3. Acute Illness / Stress
- Sepsis
- Burns
- Trauma
- Surgery
4. Chronic Kidney Disease
Reduced clearance → elevated glucagon.
5. Cirrhosis & Liver Disease
Impaired metabolism → higher glucagon.
Low Glucagon
Seen in:
- Hypothalamic/pancreatic failure
- Advanced pancreatitis
- Post-total pancreatectomy
- Genetic α-cell dysfunction
- Severe hypoglycemia from insulinoma
- Exogenous insulin overdose (impaired glucagon response)
Low glucagon can worsen severe hypoglycemia.
Reference Intervals
(Tietz 8E + Mayo + ARUP)
Values depend on fasting state and assay type.
Fasting Glucagon
- 50 – 150 pg/mL
(= 50 – 150 ng/L)
Postprandial
- Mild rise to 150–200 pg/mL
Glucagonoma
- >500 pg/mL
- Often >1000 pg/mL
Diagnostic Uses
1. Diagnosis of Glucagonoma
- Markedly elevated glucagon
- Imaging: CT/MRI/Octreoscan
- Clinical symptoms
2. Hypoglycemia Evaluation
Low glucagon response suggests:
- Insulinoma
- Pancreatic failure
- Insulin overdose
3. Diabetes Pathophysiology
Abnormal glucagon secretion contributes to:
- Fasting hyperglycemia
- Post-meal hyperglycemia
4. Assessment in Acute Illness
Stress-induced hyperglucagonemia correlates with severity.
5. Research Use
- Studies of insulin–glucagon axis
- Ketogenic diet monitoring
- Metabolic disease research
Analytical Notes
- Fasting sample required (8–10 hours)
- Place sample on ice immediately
- Use EDTA tube + aprotinin (to prevent degradation)
- Plasma preferred over serum
- Highly assay-dependent (interpret with lab reference range)
- Hemolysis and delayed processing falsely decrease glucagon
Clinical Pearls
- Glucagon is the first line of defense against hypoglycemia.
- In diabetes, glucagon is inappropriately high even after meals.
- Glucagonoma is rare but presents with a characteristic rash (NME).
- CKD elevates glucagon due to reduced clearance.
- During severe hypoglycemia, glucagon release may be impaired in long-standing diabetes.
Interesting Fact
The first glucagon radioimmunoassay in the 1950s revolutionized understanding of glucose homeostasis and paved the way for modern diabetes physiology research.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Hormones.
- Endocrine Society Guidelines - Hypoglycemia & Neuroendocrine Tumors.
- ADA Standards - Diabetes Physiology.
- Mayo Clinic Laboratories - Glucagon.
- ARUP Consult - Glucagonoma Evaluation.
- MedlinePlus / NIH - Glucagon Test.