Glucagon
Glucagon is a hormone in the body that helps maintain homeostasis, specifically regarding glucose (sugar) levels. While we sleep at night, our bodies are fasting and not taking in glucose or nutrition. Glucagon is able to maintain normal levels of blood glucose levels so that we don’t go into a state of hypoglycemia (low blood sugar).
Glucagon is secreted by alpha-cells in the pancreas in response to dipping blood glucose levels. It is also secreted in response to exercise, epinephrine and cortisol. It increases blood glucose through four actions:
Gluconeogenesis
Glycogenolysis
Lipolysis (produces substrates for gluconeogenesis
Inhibits glycogenesis (prevents consumption of glucose for storage)
There are a few things that inhibit the secretion of glucagon. These include hyperglycemia, insulin, somatostatin, and glucagon-like peptide. Insulin is the counter-regulatory hormone to glucagon and is secreted by beta-islet cells of the pancreas.
Glucagon is also available as a medication that can be used to treat hypoglycemia. But it also has an additional benefit that makes it a very useful antidote for a specific type of overdose/toxicity. Glucagon is the treatment of choice for beta-blocker toxicity. It increases levels of cyclic adenosine monophosphate (cAMP) which increases levels of intracellular calcium. An increase in Calcium leads to increased contractility and heart rate - both of which are decreased in response to beta-blockers.
