Hypoglycemia Flashcards
What is Whipple’s Triad?
Defines hypoglycemia in non-diabetic individuals as:
* Hypoglycemic symptoms
* Low blood glucose (BG) ≤55 mg/dL (3 mmol/L) during symptoms
* Resolution of symptoms with BG correction
Whipple’s Triad is essential for diagnosing hypoglycemia in patients without diabetes.
What are neurogenic symptoms of hypoglycemia?
Symptoms include:
* Palpitations
* Tremors
* Anxiety
* Hunger
* Sweating
* Paresthesias
Neurogenic symptoms are mediated by catecholamines and cholinergic mechanisms.
What are neuroglycopenic symptoms of hypoglycemia?
Symptoms include:
* Mental fogginess
* Confusion
* Irritability
* Seizures
* Loss of consciousness
* Coma
These symptoms arise from insufficient glucose supply to the brain.
What is fasting hypoglycemia?
Occurs >4 hours after meals or overnight
Fasting hypoglycemia can indicate underlying health issues.
What is postprandial (reactive) hypoglycemia?
Occurs within 4 hours after eating
Commonly seen in postgastric bypass hypoglycemia (PGBH) and noninsulinoma pancreatogenous hypoglycemia syndrome (NIPHS).
What are the causes of insulin-mediated hypoglycemia?
Causes include:
* Insulinoma
* Postgastric bypass hypoglycemia (PGBH)
* Noninsulinoma pancreatogenous hypoglycemia syndrome (NIPHS)
* Exogenous insulin or insulin secretagogues
* Factitious hypoglycemia
* Insulin autoimmune syndrome
Insulin-mediated hypoglycemia involves excess insulin production or administration.
What are the non–insulin-mediated causes of hypoglycemia?
Causes include:
* Critical illness (sepsis, hepatic/renal/heart failure)
* Starvation
* Alcohol
* Glycogen storage diseases
* Adrenal insufficiency
* Non–islet cell tumors (IGF-mediated)
Non-insulin-mediated hypoglycemia occurs due to reduced glucose production or utilization.
What is idiopathic postprandial syndrome?
Symptoms of hypoglycemia after eating without biochemical evidence
Often linked to anxiety, neuropsychiatric disorders, or stress.
What is pseudohypoglycemia?
Artifactual causes include:
* Elevated leukocyte counts
* Hemolytic anemia
* Polycythemia vera
* Discordance between capillary and venous glucose levels
Pseudohypoglycemia results from laboratory errors or conditions affecting glucose measurement.
What are counterregulatory responses to hypoglycemia?
Responses include:
* Suppression of insulin secretion
* Stimulation of glucagon and epinephrine
* Immediate hepatic glycogenolysis and gluconeogenesis
* Delayed effects from cortisol and growth hormone
These responses help restore normal blood glucose levels.
What defines hyperinsulinemic hypoglycemia?
Defined by:
* Plasma glucose ≤55 mg/dL
* Insulin ≥3 mU/mL
* C-peptide ≥0.2 nmol/L
* Proinsulin ≥5 pmol/L
* Beta-hydroxybutyrate ≤2.7 mmol/L
This condition suggests islet beta cell hyperfunction or surreptitious insulin use.
What laboratory tests are used for Whipple’s Triad?
Tests include:
* Complete blood count
* Metabolic panel
* Cortisol
* Insulin antibodies
* Serum insulin, proinsulin, C-peptide, beta-hydroxybutyrate during hypoglycemia
* Prolonged (72-hour) fast if spontaneous hypoglycemia data unavailable
* Mixed meal tolerance test (MMTT) for postprandial hypoglycemia
These tests help confirm the diagnosis of hypoglycemia.
What is postgastric bypass hypoglycemia (PGBH)?
Occurs ≥6 months after bariatric surgery with postprandial hypoglycemia and neuroglycopenic symptoms
Pathogenesis involves nesidioblastosis (islet cell hypertrophy).
What is noninsulinoma pancreatogenous hypoglycemia syndrome (NIPHS)?
Rare cause of hyperinsulinemic hypoglycemia in adults without prior bariatric surgery
Treatment includes dietary modification and medications like acarbose and diazoxide.
How can insulinoma be distinguished from factitious hypoglycemia?
Insulinoma shows:
* Elevated insulin, C-peptide, proinsulin
Factitious hypoglycemia shows:
* Elevated insulin, low C-peptide, proinsulin
* Positive sulfonylurea/meglitinide screen
This distinction is crucial for appropriate management.
What imaging techniques localize pancreatic islet cell hyperinsulinemia?
Imaging methods include:
* CT
* MRI
* PET/CT with 68Ga-DOTA-exendin-4
* Endoscopic ultrasonography for small tumors
* Selective arterial calcium infusion for occult tumors
These techniques help identify tumors responsible for hyperinsulinemia.
What is the management for inoperable insulinoma?
Management strategies include:
* Frequent feedings, snacks
* Medications: diazoxide, somatostatin analogues, verapamil, phenytoin
* Endoscopic ethanol ablation
* Chemotherapy for islet cell carcinoma
These approaches aim to control hypoglycemia and manage symptoms.
What is Multiple Endocrine Neoplasia Type 1 (MEN-1)?
An autosomal dominant condition associated with:
* Pituitary tumors
* Parathyroid tumors
* Pancreatic tumors (insulinomas, gastrinomas)
Genetic screening is recommended for family members.
What causes childhood hypoglycemia?
Causes include:
* Hyperinsulinemic hypoglycemia
* Persistent hyperinsulinemic hypoglycemia of infancy (PHHI)
* Nesidioblastosis
* Non–insulin-mediated hypoglycemia
* Inborn errors of metabolism
* Adrenal insufficiency
Childhood hypoglycemia can have various underlying metabolic causes.
What drugs can induce hypoglycemia?
Drugs include:
* Insulin
* Sulfonylureas
* Meglitinides
* Other drugs: indomethacin, quinine, pentamidine, quinolones, tramadol, cibenzoline
Awareness of medication side effects is vital in managing hypoglycemia.
What is the mechanism of alcohol-induced hypoglycemia?
Ethanol inhibits hepatic gluconeogenesis
This condition is more common in fasting or malnourished individuals with depleted glycogen stores.
What is non–islet cell tumor hypoglycemia (NICTH)?
Occurs due to large mesenchymal or epithelial tumors secreting IGF-2 or IGF-1, which bind to insulin receptors
This leads to hypoglycemia by suppressing growth hormone and glucagon.
What is autoimmune hypoglycemia?
Caused by:
* Antiinsulin receptor antibodies: mimic insulin action
* Antiinsulin antibodies: cause sudden release of free insulin
Common in Japanese patients with autoimmune diseases.
What causes hypoglycemia in critical illness?
Causes include:
* Hepatic failure: impaired gluconeogenesis and glycogenolysis
* Renal failure: reduced insulin clearance and renal glucose production
* Sepsis: increased glucose utilization and inhibited gluconeogenesis
* Starvation: depleted glycogen stores and lack of gluconeogenic substrates
Critical illness can disrupt normal glucose homeostasis.
