182b - Hypoglycemia and other Islet Issues Flashcards
What are the broad categories of hypoglycemia causes if a patient appears healthy? (2)
-
Endogenous hyperinsulinism
- Insulinoma, gastric bypass
-
Insulin autoimmune hypoglycemia
- Antibody to insulin or insulin receptor
How does hypoglycemia-associated auntomic failure (HAAF) develop?
Pts that have prologned/recurrent hypoglycemia have impaired defense mechanisms of hypoglycemia
- Insulin does not decrease
- Glucagon does not increase
-
Epinheprine does not increase: Attenuated sympathoadrenal response
- Pt is unaware of hypoglycemia - no “fight or flight” response
This predisposes the patient to more recurrent hypoglycemia
Describe the appropriate management of an insulinoma
- Surgery is curative
- But can’t always find the tumor
- Medical
- Diazoxide (–| insulin secretion)
- Octreotide (for unresectable tumors)
- Everolimus (mTOR inhibitor - advanced stage, malignant)
How do non-beta cell tumors (hepatoma, adrenocortical carinomas) predipose patients to hypoglycemia?
(non-diabetic patients)
Overprodution of “big” IGF-2
- Insulin is normally suppressed during hypoglycemia, but IGF-2 stimulates insulin receptors
- Does not complex with circulating binding proteins, so has a rapid effect on target tissues
- Incompletely processed, so it stays around for awhile
How does a patient’s risk of hypoglycemia change after an episode of hypoglycemia?
“Hypoglycemia begets hypoglycemia”
- Past episodes of hypoglycemia make a pt more likely to develop another episode of hypoglycemia
- Glucose counter-regulation mesures are further impaired (No glucagon in creased, no epinephrine increase = no behavior changes/overt symtpoms)
- “Hypoglycemia-associated autonomic failure”
List 4 physical exam findings associated with hypoglycemia
- Diaphoresis (cold sweat)
- Pallor
- Increased systolic BP
- Increased HR
- Seizure
Note: if hypoglycemis is recurrent, these symptoms may be absent
How can hypoglycemia result from inaccurate glucose measurements?
How can we prevent this?
Metabolism of glucose continues after blood draw
Use the gery top tube - separates the blood immediately, prevents leukocytosis
What hormone protects us from prolonged hypoglycemia?
Cortisol
Mobilizes energy stores
A 39 y.o. woman complains of hypoglycemic episodes day and night. She reports the need to eat frequently, every 2-3 hours and in the middle of the night and has experienced a 20 lb. weight gain in the last 6 months. Family members report she at times “acts funny”, seems disoriented and gets back to normal after eating. What is the most likely cause of his hypoglycemia?
- Starvation
- Surreptitious intake of insulin
- Insulinoma
- Binge alcohol consumption
- Sulfonylurea intake
Insulinoma
- Hungry all the time, eating often
- Acting funny = likely hypoglycemia
- Weight gain
What constitutes hypoglycemia in a person with diabetes?
Plasma glucose <70
- Even if not accompanied by typical symptoms of hypoglycemia (asymptomatic hypoglycemia)
- If BG >70, with symptoms = pseudohypoglycemia (not true hypoglycemia)
Describe the phsysiologic responses (defenses) to decreasing blood glucose (3)
Which are lost in advanced diabetes?
- Insulin levels fall
- Glucagon levels rise
- Epinephrine rises
2 and 3 are lost in advanced diabetes = less defense against hypoglycemia
What is the range for normal fasting blood glucose?
70-100
Transient rises after meals
Non-diabetics may make excursions into 50’s-60’s without issues, especially during sleep
Describe the appropriate management of a patient with post-gastric bypass hypoglycemia
-
Diet modification
- Low glycemic index, higher protein
-
Medical
- Alpha-glucosidase inhibitor (less sugar absorbed = less insulin released)
- Octreotide
-
Surgery (I think this is a last resort)
- Partial pancreatctomy
Which imaging modality has the highest sensitivity for detecting insulinomas?
Intrascopic ultrasound
(but, it’s invasive)
What is the key difference in the presentation of a patient with insulinoma vs. post-gastric bypass hypoglycemia?
- Insulinoma = fasting hypoglycemia
- Insulin levels do not lower in reponse to hypoglycemia
- Post-gastric bypass = post-prandial hypoglycemia
- Too much insulin released after a meal
What is pseudohypoglycemia?
Symptoms of hypoglycemia, even though blood glucose >70 mg
- Most common in patients with poorly controlled DM - their glucose has been high for so long, that a drop to normal causes symtpoms
- Will improve with time
Vs asymptomatic hypoglycemia, which is BG <70 without symptoms
Why is alcohol a risk factor for hypoglycemia?
Alcohol impairs gluconeogensis
- Metabolism of alcohol depletes NAD+ (causing buildup of NADH) => no NAD+ for gluconeosgenesis
Glycogenolysis is intact => takes awhile for hypoglycemia to develop
(pls correct me if wrong, biochem is a mystery to me)
How is hypoglycemia evaluated?
Whipple’s triad
- Symptoms consitent with hypoglycemia
- Low plasma glucose measured with a precise method
- Plasma, not glucose monitor
- Relief of symptoms when glucose levels normalize
A 79 y.o. man with type 2 Diabetes for 30 years, has recent developed seizures. He states that he has been taking all his medications regularly, including his mealtime insulin doses, however at times he forgets to eat. Which of the following is the most likely cause of his seizures?
- Insulin
- Brain tumor
- Insulinoma
- Binge alcohol consumption
- Starvation
a. Insulin
* Hypoglycemia caused by insulin in the absence of food intake
What are the broad categories of hypoglycemia causes if a patient appears ill? (4)
-
Drugs
- Insulin, secretagogues, alcohol
- Critical illness
-
Hormone deficiency
- Cortisol, glucagon, epinephrine
- Non-islet tumors
Note: insulinoma is an islet tumor
