Hypoglycemia/Insulinoma Flashcards
What is the definition of Hypoglycemia?
Plasma glucose low enough to cause signs or symptoms
Impairment of brain function
<70 mg/dl
What is Whipple’s Triad?
- Symptoms/signs consistent w/ hypoglycemia
- Low measured plasma glucose concentration
- Resolution of symptoms/signs w/ increasing plasma glucose
What is the counter-regulatory hormone response to hypoglycemia?
know table on slide 5
What are the signs & symptoms of hypoglycemia?
-
Neurogenic (autonomic)
- Tremor
- Palpitations
- Anxiety/arousal
- Sweating
- Hunger
-
Neuroglycopenic (most concerning)
- Cognitive impairment
- Behavioral changes
- Psychomotor abnormalities
- Visual changes
- Seizures
- Coma
What is the differential diagnosis for Hypoglycemia? (5)
-
Drugs
- Insulin
- Insulin secretogogue
-
Critical Illness
- Liver, kidney, heart failure
- Sepsis
- Severe malnourishment
-
Hormone Deficiency
- Cortisol
-
Endogenous Hyperinsulin
- Insulinoma
- Nesidioblastosis
- Post-gastric bypass
-
Insulin Autoimmune
- Antibody to insulin
- Antibody to insulin receptor
What is an Insulinoma?
Epidemiology?
Distribution?
- Insulin-secreting tumors of pancreatic origin that cause hypoglycemia
- 1-4 people per million
- 1-2% of all pancreatic neoplasms
- Benign, solitary, intrapancreatic, <2 cm (90%)
- Evenly distributed throughout the pancreas
Insulinoma diagnosis is made per ________ studies when ________.
Hormonal
Hypoglycemic
Imaging helps to localize the insulinoma ______ the diagnosis is made.
After
How is a supervised fast used to diagnose insulinoma?
- Provoke hormonal responses that maintain Euglycemia
- Normally symptomatic hypoglycemia should not occur after a prolonged fast given gluconeogenesis
- Up to 72 hr fast can be used to determine the presence & etiology of hypoglycemia
What are the end points for the supervised fast test?
- Glucose < 45 mg/dl
- Signs/symptoms of hypoglycemia
- > 72 hrs have elapsed
- Glucose < 55 mg/dl + Whipple’s triad
C-peptide is a marker for ___________.
endogenous insulin secretion
What are the cutoffs for patients w/ insulinomas after a 72 hr fast?
Glucose < 55 mg/dl
Insulin > 3 μU/ml
What are the 6 markers used to determine the etiology of hypoglycemia after a 72 hr fast?
- Insulin
- C-peptide
- Sulfonylurea screen
- Pro-insulin
- ß-hydroxybutyrate
- Response to 1 mg IV glucagon
Hypoglycemia
Insulin after 72 hr fast
- < or > 3 μU/ml
- Insulin-mediated will have elevated insulin concentrations
- Increased insulin: insulinomas, sulfonylureas, insulin autoimmune, exogenous insulin
Hypoglycemia
C-peptide after 72 hr fast
- < or > 0.2 nmol/l
- Exogenous (pharmacologic) insulin does not contain C-peptide
- Sulfonylureas & insulinomas will increase insulin & C-peptide
Hypoglycemia
Sulfonylureas after 72 hr fast
Screen blood as sulfonylureas use & insulinoma could otherwise be indistinguishable (both raise insulin & C-peptide)
Hypoglycemia
ß-hydroxybutyrate after 72 hr fast
- Insulin has anti-ketogenic effect
- Insulinoma patients have lower levels when fasting
- End of fast = < 2.7 mmol/l
- Progressive rise after 18 hrs could also indicate negative fast
Hypoglycemia
Response to IV glucagon after 72 hr fast
- Insulin is anti-glycogenolytic
- Hyperinsulinemia permits the retention of glycogen w/i the liver
- Patients w/ insulin-mediated hypoglycemia respond to 1 mg of IV glucagon w/ a subsequent increase in plasma glucose at the end of a supervised fast
What is the Mixed Meal Test?
When is it used?
- Not standardized & validated like 72 hr fast
- Used to evaluate patients w/ postprandial symptoms
- Measure glucose, pro-insulin, insulin & C-peptide pre-meal (fasting) and every 30 min post-meal (mixture fats, carbs, protein)
- Trying to confirm if hypoglycemia is an etiology of the symptoms & clarify if insulin mediated
- Helpful in patients w/ postprandial symptoms following for example, GI procedures (Roux en Y gastric bypass surgery)
