What is cholecystokinin (CCK)?

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Last updated: October 3, 2026 • View editorial policy

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What is Cholecystokinin (CCK)?

Cholecystokinin (CCK) is a 33 amino acid polypeptide hormone produced endogenously in the proximal small bowel that serves as the principal hormone controlling gallbladder emptying after meals. 1

Primary Physiological Functions

CCK is released into the bloodstream after ingestion of meals, particularly those containing protein and fat 1. The hormone exerts its effects through two main mechanisms:

Biliary System Actions

  • Gallbladder contraction: CCK binds to receptors in the gallbladder causing contraction
  • Sphincter of Oddi relaxation: CCK binds to receptors on inhibitory neurons innervating the sphincter, causing relaxation and leading to increased bile flow into the intestine 1

Additional Gastrointestinal Effects

  • Inhibition of gastric emptying
  • Suppression of appetite (first identified intestinal satiety signal to the brain)
  • Increased intestinal peristalsis (responsible for abdominal cramping after rapid intravenous infusion) 1

Molecular Structure and Clinical Formulation

The c-terminal octapeptide of CCK represents the physiologically active portion, which was first isolated and synthesized in 1970 1. Its analogue, sincalide, is the only commercially available drug in clinical use for CCK-cholescintigraphy (CCK-CS) 1.

Broader Biological Significance

Beyond its classical gut hormone functions, CCK is now recognized as the most abundant neuropeptide in the human brain 2, 3. The CCK gene is expressed in multiple tissue types including:

  • Central and peripheral neurons
  • Extra-intestinal endocrine cells
  • Immune cells
  • Cardiomyocytes
  • Spermatogenic cells
  • Certain fat cells 2

This widespread expression means CCK functions not only as a hormone but also as a neurotransmitter, paracrine growth factor, satiation factor, anti-inflammatory cytokine, incretin, adipokin, and myokin 2.

Clinical Applications

CCK testing (CCK-CS) is primarily used to evaluate functional gallbladder disorder (FGBD) in patients with biliary-type pain and an ultrasonographically normal gallbladder 1. The test measures gallbladder ejection fraction (GBEF) after CCK stimulation, with abnormally low values indicating gallbladder dysfunction 1.

Emerging Therapeutic Areas

Recent research suggests potential therapeutic applications in:

  • Metabolic disorders (obesity, eating disorders, type 2 diabetes) 2, 4
  • Neuropsychiatric diseases (memory and anxiety disorders) 2, 5
  • Cardiac disease prognosis 2
  • Neuroendocrine tumors 2

References

2
Research

Cholecystokinin: Clinical aspects of the new biology.

Journal of internal medicine, 2025

3
Research

Clinical endocrinology and metabolism. Cholecystokinin.

Best practice & research. Clinical endocrinology & metabolism, 2004

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.