[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › [Endocrine](https://durgical.com/en/physiology/#s-endocrine) › Glucagon and the counter-regulatory hormones

[Physiology](https://durgical.com/en/physiology/) · [Endocrine](https://durgical.com/en/physiology/#s-endocrine)

# Glucagon and the counter-regulatory hormones

- Regulation
- Exam priority: medium

When glucose falls, glucagon and epinephrine raise it within minutes; cortisol and GH hold it up for hours.

Updated 2026-11-01

Also called: α cell, Defense against hypoglycemia

**See it in 3D:** [Pancreas](https://durgical.com/en/anatomy/pancreas/) · [Liver](https://durgical.com/en/anatomy/liver/)

## Key points

- Order as glucose falls: insulin drops first, then glucagon and epinephrine rise, then cortisol and GH (hours).
- Glucagon acts on the liver (not muscle, which lacks the receptor): glycogenolysis, gluconeogenesis and ketogenesis.
- It is stimulated by hypoglycemia, amino acids and the sympathetic system; it is braked by glucose, insulin and somatostatin.
- A protein-only meal releases insulin AND glucagon: glucagon keeps insulin from causing hypoglycemia.
- After some years of type 1 diabetes the glucagon response is lost and epinephrine becomes the main defense.

## What it is

Counter-regulatory hormones oppose insulin and protect the brain from hypoglycemia. Glucagon from α cells acts almost only on the liver: it releases glucose from glycogen, makes new glucose and, in long fasting, ketones. Epinephrine, cortisol and GH complete the defense on different time scales. The signal pathway (Gs-coupled receptor, cAMP, PKA) is in Biochemistry.

## Regulation

- *+* **Hypoglycemia**: Main stimulus of α cells.
- *+* **Amino acids (alanine, arginine)**: Raise glucagon after a protein meal.
- *+* **Sympathetic nerves and epinephrine (β2)**: Increase glucagon in exercise and stress.
- *−* **Insulin and zinc from neighboring β cells**: Paracrine inhibition within the islet.
- *−* **High glucose**: Suppresses secretion.
- *−* **Somatostatin**: Inhibits α and β cells.

## The stepwise defense against hypoglycemia

| Hormone | Glucose at which it responds (approx.) | Speed | Main action |
| --- | --- | --- | --- |
| Insulin (falls) | ≈80–85 mg/dL | Minutes | Stops braking hepatic glucose output |
| Glucagon (rises) | ≈65–70 mg/dL | Minutes | Hepatic glycogenolysis and gluconeogenesis |
| Epinephrine (rises) | ≈65–70 mg/dL | Minutes | Glycogenolysis, lipolysis, ↓ insulin; adrenergic symptoms |
| Cortisol and GH (rise) | ≈65–70 mg/dL | Hours | Gluconeogenesis and less peripheral glucose use |

## Clinical notes

- Warning symptoms (tremor, sweating, palpitations, hunger) appear near ≈55 mg/dL; below 50 mg/dL neuroglycopenic ones dominate (confusion, seizures).
- Hypoglycemia unawareness: repeated episodes lower the epinephrine threshold and the patient loses the warning symptoms.
- Beta-blockers can mask the adrenergic symptoms of hypoglycemia (not sweating, which is cholinergic).

## Memory aid

Insulin stores, glucagon pulls out: one fills the liver's pantry, the other empties it when the brain is hungry.

## Test yourself

Think of the answer, then tap the question to see it.

## Why doesn't glucagon release glucose from muscle glycogen?

Muscle has no glucagon receptor and no glucose-6-phosphatase; its glycogen is mobilized by epinephrine and used by the muscle itself.

## Why does a protein-rich, carbohydrate-free meal stimulate both insulin and glucagon?

Amino acids stimulate both cell types; insulin lets the amino acids be used and glucagon keeps hepatic glucose output going, preventing hypoglycemia.

## Why is a patient with long-standing type 1 diabetes more vulnerable to severe hypoglycemia?

The glucagon response to hypoglycemia is lost and, with repeated episodes, the epinephrine response also weakens; the fast defenses are gone.

## Why can't cortisol and GH correct acute hypoglycemia?

They act through changes in gene expression and peripheral metabolism; their effect takes hours, useful in prolonged fasting but not within minutes.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/physiology/glucagon-and-the-counter-regulatory-hormones/)

## See it in 3D

The structures of Durgical's 3D anatomy where it happens.

- [Pancreas](https://durgical.com/en/anatomy/pancreas/)
- [Liver](https://durgical.com/en/anatomy/liver/)

## Related topics

- [Islets and insulin: secretion and actions](https://durgical.com/en/physiology/islets-and-insulin-secretion-and-actions/)
- [The physiological response to hypoglycemia](https://durgical.com/en/physiology/the-physiological-response-to-hypoglycemia/)
- [Physiology of diabetes and ketoacidosis](https://durgical.com/en/physiology/physiology-of-diabetes-and-ketoacidosis/)
- [Actions of cortisol](https://durgical.com/en/physiology/actions-of-cortisol/)
- [The adrenal medulla and catecholamines](https://durgical.com/en/physiology/the-adrenal-medulla-and-catecholamines/)
- [Fed and fasting states: the hormonal switch](https://durgical.com/en/physiology/fed-and-fasting-states-the-hormonal-switch/)

## Related conditions

- [Type 1 diabetes mellitus](https://durgical.com/en/conditions/type-1-diabetes-mellitus/)
- [Diabetic ketoacidosis](https://durgical.com/en/conditions/diabetic-ketoacidosis/)

## In Biochemistry

- [Glucagon signalling](https://durgical.com/en/biochemistry/topics/glucagon-signalling/)
- [Gluconeogenesis](https://durgical.com/en/biochemistry/pathways/gluconeogenesis/)
- [Glycogen metabolism](https://durgical.com/en/biochemistry/pathways/glycogen-metabolism/)
- [G protein-coupled receptors and cAMP](https://durgical.com/en/biochemistry/topics/g-protein-coupled-receptors-and-camp/)

## In Pharmacology

- [Insulins](https://durgical.com/en/pharmacology/classes/insulins/)

[← All of physiology](https://durgical.com/en/physiology/)

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: [17.9 The Endocrine Pancreas](https://openstax.org/books/anatomy-and-physiology-2e/pages/17-9-the-endocrine-pancreas) (OpenStax (Rice University), 2022); [Hypoglycemia: MedlinePlus](https://medlineplus.gov/hypoglycemia.html) (MedlinePlus, US National Library of Medicine, 2024); [Type 1 Diabetes](https://www.ncbi.nlm.nih.gov/books/NBK507713/) (StatPearls (NCBI Bookshelf), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 79). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/physiology/glucagon-and-the-counter-regulatory-hormones/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/glucagon-and-the-counter-regulatory-hormones/