InsulinSecreted only by pancreas

First synthesized polypeptide hormone

1

www.medicinemcq.com

I to 2 million islets of Langerhans

Islet formation in the fetusStarts by 10 weeks

Islets of Langerhans

2

Three major types of cellsAlpha

Beta

Delta cells

www.medicinemcq.com

Islets

3

4www.medicinemcq.com

Constitute 70 %

Secrete insulin and amylin

Beta cells

5

Anabolic

Insulin

6

20% of the total islets

Secrete glucagon

Alpha cells

7

Catabolic

www.medicinemcq.com

Glucagon

8

Liver

Main site of action of insulin and glucagon

9

50% degraded by the liver

50% enters the systemic circulation

Binds to insulin receptors

Insulin secreted into the portal vein

10

2 amino acid chains linked by disulphide bridges

www.medicinemcq.com

Insulin is a polypeptide

11

12www.medicinemcq.com

Stored together

Co-secreted from the beta cells

Insulin and C peptide

13

Connecting peptide

Connects A and B segments of insulin

Facilitates folding to form proinsulin

C peptide has no other action

C peptide

14

15www.medicinemcq.com

C peptideReleased in equal amounts as that of insulin.

Index of B cell function.

www.medicinemcq.com

Index of B cell function

16

Useful marker of insulin secretion

Less susceptible than insulin to hepatic degradation

C peptide

17

Main regulator of insulin secretion by the pancreatic beta cells

Glucose

18

Controls glucose-regulated insulin secretion

Rate-limiting step

Glucokinase

19

Stimulate insulin synthesis and insulin secretion

For rest of the slides, visit www.medicinemcq.com >

Diabetes Mellitus

Glucose > 70 mg/dL

20