Cholecystokinin-33

Where it comes from

Made in

I cells of the upper small intestine

Sent out by

Fat and protein after a meal

Acts on

• Gallbladder
• Pancreas
• Vagus nerve

What it does

• Contracts the gallbladder and drives enzyme secretion, as the shorter forms do
• Longer-lived in blood than CCK-8, so one meal’s signal lasts longer
• The predominant cholecystokinin in human plasma and intestine, which form-specific assays settled in 2001 ¹

In medicine

• Counted in “total CCK” assays; no medicine copies this form
• Because it dominates, a “CCK level” reported in a human study is mostly this peptide, whatever the paper calls it ¹

Beyond the body’s own use

• Not studied apart from the CCK family, and no analogue of this length has been taken into a trial
• What is asked of CCK now is whether its receptors can be used to image and treat tumours that carry them; that work runs through the receptor and not through any one length of the hormone ²