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Human Body Study

Pancreatic / Glucose Axis

The pancreatic / glucose axis Pancreatic islets sense blood glucose directly. β-cells release insulin when glucose rises, driving tissue uptake and storage to lower it. α-cells release glucagon when glucose falls, driving hepatic glucose output to raise it. δ-cell somatostatin acts as a local brake on both. The diagram is a closed substrate-feedback loop with glucose at the centre. Pancreatic islets β · insulin α · glucagon δ-cells: somatostatin (local brake on both) Muscle · adipose · liver ↑ glucose uptake ↑ glycogen / lipid synthesis Liver glycogenolysis gluconeogenesis Blood glucose regulated variable ~70–110 mg/dL insulin glucagon ↓ glucose ↑ glucose ↑ glucose → β-cells fire ↓ glucose → α-cells fire Substrate feedback: glucose level is its own input. Counter-regulatory backup: cortisol, GH, epinephrine. Amylin (co-secreted with insulin) and incretins (GLP-1, GIP) modulate the response.

Signaling chain

Section titled “Signaling chain”

A pituitary-independent system centered on the pancreatic islets of Langerhans:

  • Insulin — β-cells; released when blood glucose rises.
  • Glucagon — α-cells; released when blood glucose falls.
  • Somatostatin — δ-cells; locally inhibits both insulin and glucagon.
  • Amylin (co-secreted with insulin) and incretins (GLP-1, GIP) modulate the response.

Function

Section titled “Function”

Maintains blood glucose within a narrow range. Insulin is the body’s main anabolic hormone — it drives glucose uptake into muscle and fat, promotes glycogen, lipid, and protein synthesis, and suppresses hepatic glucose output. Glucagon is counter-regulatory — it stimulates hepatic glycogenolysis and gluconeogenesis to raise glucose.

Feedback

Section titled “Feedback”

Direct substrate feedback: glucose levels themselves regulate hormone release. Cortisol, GH, epinephrine, and glucagon together form the counter-regulatory defense against hypoglycemia.

Clinical relevance

Section titled “Clinical relevance”
  • Type 1 diabetes — autoimmune β-cell destruction, absolute insulin deficiency.
  • Type 2 diabetes — insulin resistance with relative insulin deficiency.
  • Hypoglycemia — insulinoma, drug effect, counter-regulatory failure.
  • Major drug classes: insulin, metformin, sulfonylureas, GLP-1 agonists, SGLT2 inhibitors, DPP-4 inhibitors.

Key labs

Section titled “Key labs”

Fasting glucose, HbA1c, oral glucose tolerance test, C-peptide, fasting insulin, autoantibodies (GAD, IA-2) for type classification.