30: Clinical Endocrinology Flashcards
What is the honeymoon period in T1DM?
The period of time following diagnosis where the pancreas can produce a significant amount of insulin to reduce insulin needs (~10% remaining)
What are the counter regulatory hormones to insulin?
- Glucagon
- Catecholamines
- Cortisol
- Growth hormone
What are the actions of insulin?
ANABOLIC
Stimulates: glucose uptake, glycolysis glycogen synthesis, protein synthesis, uptake of ions
Inhibits: gluconeogenesis, glucogenolysis, lipolysis, ketogenesis, proteolysis
Why are fluctuations in blood sugar throughout the day important?
Creates gradients that allow glucose to enter the cell (aid uptake)
What is the mechanism of action of insulin
- 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
Where does energy at birth come from?
20% from metabolising ketones
What is the mechanism of ketone production?
- White fat - activation of hormone sensitive lipase causes lipolysis of triglycerides (inhibited by INSULIN)
- Liver - NEFA taken up by hepatocytes, undergoes oxidation to Acetyl CoA
- Mitochonrdia - Acetyl CoA broken down into ketones
What are the 3 important ketones?
- Acetoacetate
- Beta hydroxybutyrate
- Acetone
Ketones require ____ + ___
Lack of insulin + excess glucagon
How does DKA affect the ion gap?
- Increases
- Dissociation of acids means H+ free to bind to bicarbonate (CO2 and H2O)
Why might a patient being treated for DKA have hyperchloremia?
- Fluid replacement with 0.9% NaCl
- Salt loading and normalising of Na (salt lost in urine) but no net loss of Cl - causes hyperchloremia
Why does urine testing with a ketone strip tend to underestimate the extent of acidosis in DKA?
- Reaction occurs in the presence of acetoacetate
- In DKA AcAc pushed to BOHB (less to react and cause colour change)
Why are bedside tools poor for measuring severe acidosis?
Too saturated
Where is the majority of intracellular K stored?
Muscle
K is regulated with a feed___ mechanism
Forward - does not rely on serum levels to trigger reaction
How do:
- Insulin
- cAMP and glucagon
- Aldosterone
Affect serum K
- 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
Acidosis increases/decreases K loss from cells
Increases
What effect can beta blockers have on K levels?
- Prevent muscle reuptake
- Inc s[K]
What are the 3 determining factors of K secretion?
- Activity of Na/K/ATPase
- Permeability of luminal membrane
- Electrochemical gradient from lumen -> blood
Why do a lot of diuretics decrease serum K?
Inc. distal tubular flow results in decreased serum K
