30: Clinical Endocrinology

Question 1

What is the honeymoon period in T1DM?

Answer 1

The period of time following diagnosis where the pancreas can produce a significant amount of insulin to reduce insulin needs (~10% remaining)

Question 2

What are the counter regulatory hormones to insulin?

Answer 2

• Glucagon
• Catecholamines
• Cortisol
• Growth hormone

Question 3

What are the actions of insulin?

Answer 3

ANABOLIC

Stimulates: glucose uptake, glycolysis glycogen synthesis, protein synthesis, uptake of ions

Inhibits: gluconeogenesis, glucogenolysis, lipolysis, ketogenesis, proteolysis

Question 4

Why are fluctuations in blood sugar throughout the day important?

Answer 4

Creates gradients that allow glucose to enter the cell (aid uptake)

Question 5

What is the mechanism of action of insulin

Answer 5

• Bind to insulin receptor on cell
• Stimulates translocation of GLUT4 to cell surface
• Allows glucose to be taken up by the cell via passive diffusion
• Stimulate glycogen syntehsis, fatty acid synthesis

Question 6

Where does energy at birth come from?

Answer 6

20% from metabolising ketones

Question 7

What is the mechanism of ketone production?

Answer 7

1. White fat - activation of hormone sensitive lipase causes lipolysis of triglycerides (inhibited by INSULIN)
2. Liver - NEFA taken up by hepatocytes, undergoes oxidation to Acetyl CoA
3. Mitochonrdia - Acetyl CoA broken down into ketones

Question 8

What are the 3 important ketones?

Answer 8

• Acetoacetate
• Beta hydroxybutyrate
• Acetone

Question 9

Ketones require ____ + ___

Answer 9

Lack of insulin + excess glucagon

Question 10

How does DKA affect the ion gap?

Answer 10

• Increases

- Dissociation of acids means H+ free to bind to bicarbonate (CO2 and H2O)

Question 11

Why might a patient being treated for DKA have hyperchloremia?

Answer 11

• Fluid replacement with 0.9% NaCl

- Salt loading and normalising of Na (salt lost in urine) but no net loss of Cl - causes hyperchloremia

Question 12

Why does urine testing with a ketone strip tend to underestimate the extent of acidosis in DKA?

Answer 12

• Reaction occurs in the presence of acetoacetate

- In DKA AcAc pushed to BOHB (less to react and cause colour change)

Question 13

Why are bedside tools poor for measuring severe acidosis?

Answer 13

Too saturated

Question 14

Where is the majority of intracellular K stored?

Answer 14

Muscle

Question 15

K is regulated with a feed___ mechanism

Answer 15

Forward - does not rely on serum levels to trigger reaction

Question 16

How do:

• Insulin
• cAMP and glucagon
• Aldosterone

Affect serum K

Answer 16

• Insulin stimulates Na/K/ATPase and inc. K uptake
• cAMP and glucagon stimulated by protein rich meal, shift transtubular K gradient and inc. GFR
• Aldosterone promotes K uptake by cells and renal excretion

Question 17

Acidosis increases/decreases K loss from cells

Answer 17

Increases

Question 18

What effect can beta blockers have on K levels?

Answer 18

• Prevent muscle reuptake

- Inc s[K]

Question 19

What are the 3 determining factors of K secretion?

Answer 19

1. Activity of Na/K/ATPase
2. Permeability of luminal membrane
3. Electrochemical gradient from lumen -> blood

Question 20

Why do a lot of diuretics decrease serum K?

Answer 20

Inc. distal tubular flow results in decreased serum K