Hypoglycemia

Question 1

name normal blood glucose levels

Answer 1

• fasting: 70-110 mg/dL
• 2 hours postprandial: <120 mg/dL
• if <55 mg/dL
  
  • results in hypoglycemia with adrenergic or neuroglycopenia

Question 2

the half-life of insulin and glucose is ~___ min

Answer 2

4-6 min

Question 3

post-prandial increase of glucose leads to increase of _____ and decrease of _____

Answer 3

post-prandial increase of glucose leads to increase of insulin and decrease of glucagon

Question 4

the ____ level drops only 25% and is ready to be raised during fasting

why is _____ always present?

Answer 4

the glucagon level drops only 25% and is ready to be raised during fasting

hypoglycemia is much worse than hyperglycemia, always have basal levels of glucagon since you don’t want to waste time synthesizing it in times of need

Question 5

describe the synthesis of insulin

Answer 5

preproinsulin -> proinsulin -> human insulin

• preproinsulin has disulfide side groups that need help connecting and creating disulfide bonds
• the leader sequence is cleaved and this creates proinsulin that has disulfide bonds
• C-peptide is cleaved in proinsulin to make human insulin

Question 6

describe the function of the C-peptide

Answer 6

helps to form the disulfide bonds with precision

• the A-chain has 2 adjacent cysteine residues
  
  • the first forms the intrachain disulfide bond in the A-chain
  • the second forms the interchain disulfide bond with the B-chain

Question 7

describe the function of the liver after a meal

Answer 7

• uptake of dietary sugars slows down the increase of blood glucose
• insulin stimulates hepatic:
  
  • glycogen synthesis
  • fatty acids synthesis
  • cholesterol synthesis

Question 8

describe the function of the liver during fasting

Answer 8

• release of free glucose into the blood prevents drop of blood glucose
• glucagon stimulates hepatic:
  
  • glycogen degradation
  • gluconeogenesis
  • fatty acid degradation

Question 9

glycogen is the storage form of glucose and is found in _____

Answer 9

glycogen is the storage form of glucose and is found in cytosolic glycogen granules

Question 10

glycogen degradation is stimulated by _____ and _____

Answer 10

• glucagon and epinephrine

Question 11

the _____ structure of glycogen allows rapid release of many free glucose molecules into the blood

Answer 11

the branched structure of glycogen allows rapid release of many free glucose molecules into the blood

Question 12

what is needed for gluconeogenesis

Answer 12

• alanine, lactate and glycerol (provided by the blood)

Question 13

during fasting, which 2 organs perform gluconeogenesis?

Answer 13

liver and kidney

Question 14

low blood glucose levels activate which systems?

Answer 14

• pituitary gland release ACTH -> cortisol (gluconeogenesis)
• autonomic nervous system releases catecholamines (glycogenolysis) and glucagon (both glycogenolysis and gluconeogenesis)
• alpha-cells of the pancreas release glucagon

Question 15

describe adrenergic symptoms

Answer 15

• occurs abruptly when the blood glucose levels fall
  
  • epinephrine is released and is stimulated by the regulation of the hypothalamus
• symptoms:
  
  • anxiety
  • palpitation
  • tremors
  • sweating

Question 16

describe neuroglycopenia symptoms

Answer 16

• occurs from a gradual decline
  
  • the slow decline deprives the brain of glucose but fails to trigger the epinephrine response
• symptoms:
  
  • headache
  • confusion
  • slurred speech
  • coma and death

Question 17

describe insulin injection induced hypoglycemia

Answer 17

• diabetic patients can accidentally inject too much insulin
  
  • activated GLUT-4 lead to glucose uptake into muscle and fat –> hypoglycemia
• mild treated with OJ, juice, carbs
• severe treated with glucagon to stimulate glycogenolysis

Question 18

describe reactive postprandial hypoglycemia

Answer 18

• exaggerated insulin release following a big meal
  
  • leads to increased uptake of glucose into muscle + fat
• small meals recommended

Question 19

describe hypoglycemia hepatic genetic diseases

Answer 19

• genetic defects of hepatic enzymes of glycogen degradation and gluconeogenesis lead to reduced release of glucose into the blood during fasting
• abnormal metabolism of dietary fructose and galactose impairs gluconeogenesis

Question 20

describe alcohol-related fasting hypoglycemia

Answer 20

• common in undernourished, longer fasting or dehydrated individuals after consumption of many drinks with high alc.
• ethanol metabolism in the liver uses NAD+ and forms NADH which leads to an abnormal high NADH/NAD+ ratio
  
  • reduces gluconeogenesis

Question 21

describe insulinoma

Answer 21

• tumor of the pancreatic islet cells
• over activates GLUT-4 transporters in muscle and fat cells

Question 22

contrast blood levels of endogenous insulin synthesis vs exogenous insulin synthesis

Answer 22

• endogenous:
  
  • insulin (high)
  • C-peptide (high)
• exogenous:
  
  • insulin (high)
  • c-peptide (low)
  • proinsulin (absent)

Question 23

how do you diagnose factitious hypoglycemia due to insulin injection

Answer 23

• high levels of insulin
• low levels of C-peptide
• (absence of proinsulin)
• (absence of sulfonylurea)

Question 24

how do you diagnose factitious hypoglycemia due to sulfonylurea tablet ingestion

Answer 24

sulfonylurea stimulates endogenous insulin synthesis and secretion from pancreas

• high level of insulin
• high level of C-peptide
• presence of proinsulin
• presence of sulfonylurea

Question 25

_______ is the most severe form of Factitious disorder

Answer 25

Munchausen Syndrome