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ENDOCRINOLOGY > Hypoglycemia > Flashcards

Hypoglycemia Flashcards

1
Q

Draw and label a beta cell

A
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2
Q

List 5 genetic causes of hyperinsulinism

A
  • KATP-HI: ABCC8 (SUR1 subunit) or KCNJ11 (KIR6.2 subunit)
  • Glutamate dehydrogenase-HI: GLUD1
  • Glucokinase-HI: GCK - 3-hydroxy-acylCoA dehydrogenase deficiency: HADH
  • Exercise-induced HI: SLC16A1 (transporter MCT1)
  • HNF4A
  • HNF1A
  • Mitochondrial uncoupling protein HI: UCP2
  • Mosaic Beckwith Weidemann
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3
Q

List 3 acquired causes of hyperinsulinism

A
  • Infant of a diabetic mother
  • Peripartum stress HI
  • Insulinoma (sporadic or MEN1)
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4
Q

What is baby’s size in GCK hyperinsulinism?

A

AGA if mother is affected

LGA if mother is unaffected

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5
Q

What is the pathophysiology of GCK hyperinsulinism?

A

Lowering of beta cell “glucosensor”

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6
Q

In exercise-induced hyperinsulinism, how quickly does hypoglycemia occur?

A

Within 30 minutes of strenuous exercise (ex swimming)

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7
Q

Which HNF mutation has HI plus Fanconi tublulopathy?

A

HNF4A

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8
Q

What is the inheritance of diffuse and focal KATP HI?

A

Diffuse: recessive (less commonly dominant)

Focal: inheritance of a paternal mutation (second hit is the loss of maternal allele)

  • In close proximity to KATP gene are 2 tumor suppressor genes (H19 and CDKN1c) and a paternally expressed growth factor gene (IGF2). Therefore growth advantage after loss of maternal allele
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9
Q

Is focal HI visible on routine imaging (ultrasound, CT, MRI)?

A

No (unlike insulinoma)

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10
Q

What proportion of kids with KATP-HI are responsive to diazoxide?

A

30% (Dominant inheritance may be more responsive)

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11
Q

Name 2 types of genetic hyperinsulinism that cause protein-induced hypoglycemia

A
  • Glutamate dehydrogenase (GDH) aka HI-HA
  • HADH (3-hydroxyacyl-CoA dehydrogenase)
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12
Q

What test can localize a lesion in focal KATP-HI?

A

Fluorine-18 labelled fluoro-L-DOPA PET scan Intraoperative biopsies and examination by pathology

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13
Q

How long should kids be able to fast for, by age?

A
  • 1 week to 1 year: 15-24 (or 18) hours
  • 1-5 years: 24 hours
  • >5 years: 36 hours
  • Adults: 48-72 hours
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14
Q

How does diazoxide work?

A

Maintains KATP channel in open position, suppressing insulin release

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15
Q

What are the side effects of diazoxide?

A
  • Fluid retention
  • Leukopenia (rare)
  • Thrombocytopenia (rare)
  • Pulmonary hypertension (rare)
  • Long term: hypertrichosis, coarsening of face
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16
Q

How does octreotide work?

A
  • Somatostatin analogue. Suppresses insulin downstream of voltage-gated calcium channel
  • Other facts about octreotide: Subcutaneous injection. Tachyphylaxis develops
17
Q

Name 2 ways to diagnose GDH-HI (aka HI-HA)

A
  • Genetic testing of GLUD1 gene
  • Acute insulin response to leucine-loading test
18
Q

When does GCH-HI (aka HI-HA) present?

A

Later in infancy, when higher-protein foods and longer periods of fasting are introduced. Usually 4-12 months of age.

19
Q

List clinical features of Beckwith-Wiedemann Syndrome

A
  • Macroglossia
  • Omphalocele
  • Hemihypertrophy
  • Renal malformations
  • Hyperinsulinism (mechanism is not clear)
  • Predisposition to embryonal tumors (Wilms, hepatoblastoma)
20
Q

What is the mechanism for hypoglycemia in an infant of a diabetic mother?

A
  1. Hyperglycemia in mother
  2. Infant appropriately upregulates insulin secretion (macrosomia develops)
  3. Glucose supply is abruptly interrupted at birth, hypoglycemia develops
  4. Counter-regulatory glucagon and epinephrine are diminished due to immaturity of these axes
21
Q

Where are the four GLUT transporters found?

A
  • GLUT1: blood-brain barrier
  • GLUT2: pancreatic islets, liver
  • GLUT3: brain and others
  • GLUT4: adipocytes, muscle
22
Q

What are the 3 metabolic systems that regulate response to fasting?

A
  1. Hepatic glycogenolysis (stimulated by glucagon and epinephrine)
  2. Hepatic gluconeogenesis (using amino acids from muscle protein)
  3. Hepatic ketogenesis (fatty acid oxidation; ketones used by brain and muscle)
23
Q

What is Whipple’s triad?

A
  1. Signs and symptoms of hypoglycemia
  2. Low BG (<2.8)
  3. Resolution of symptoms after BG increased
24
Q

What are factors that can affect measurement of BG?

A
  • Whole blood vs plasma (plasma 10-15% higher)
  • Time to sample measurement (more time = lower BG due to glycolysis by RBC and WBC)
  • Glucometers (inadequate sample = false low)
  • Sampling from line without adequate flush
25
Q

Name 5 neurogenic symptoms of hypoglycemia (around 3 mmol/L)

A
  • Shakiness, trembling, jitteriness (infants)
  • Sweating
  • Tachycardia
  • Hunger
  • Anxiety/nervousness
  • Weakness
  • Nausea/vomiting
  • Pallor (infants)
  • Hypothermia (infants)
26
Q

Name 5 neuroglycopenic symptoms of hypoglycemia (<2.8 mmol/L)

A
  • Lethargy
  • Irritability, restlessness
  • Confusion
  • Headache, visual disturbance
  • Seizures
  • Poor feeding (infants)
  • Tachypnea
  • Apnea, cyanosis
  • Weak/high-pitched cry (infants)
  • Low tone, floppiness
  • Eye rolling, lip smacking (infants)
  • Loss of consciousness, coma
27
Q

Why are babies with congenital hyperinsulinism born LGA?

A

Growth promoting effects of insulin in utero

28
Q

Diagnostic criteria for hyperinsulinism? (Lab-based)

A
  • Elevated plasma insulin (>2 micromol/mL)
  • Low free fatty acids (<1.5 mmol/L)
  • Low ketones (BOHB <2.0 mmol/L)
  • Glycemic response to 1mg IV glucagon (>30 mg/dl or 1.7 mmol/L)
29
Q

What are the three genetic types of KATP hyperinsulinism? Do they respond to diazoxide?

A
  1. Recessive, diazoxide unresponsive (most common). Essentially a complete absence of channels.
  2. Dominant, diazoxide responsive
  3. Dominant, diazoxide unresponsive
30
Q

What are the actions of insulin, glucagon, epinephrine, GH and cortisol on glycogneolysis, gluconeogenesis, lipolysis and ketogenesis?

A
31
Q

What drugs can cause hypoglycemia?

A
  • Oral hypoglycemics (sulfonylureas)
  • Beta blockers
  • Insulin
  • Ethanol
  • Salicylates
  • Quinine
  • Unripe ackee fruit
32
Q

What are the components of a critical sample?

A
  • Glucose
  • Insulin
  • Beta-hydroxybutyrate
  • Free fatty acids
  • Growth hormone
  • Cortisol
  • Acylcarnitine profile
  • Plasma amino acids
  • Uric acid, ammonia, lactate
  • Urine: organic acids, urinalysis
33
Q

Critical sample in: Insulinoma vs Adrenal Insufficiency vs Glyburide vs Exogenous Insulin

A
34
Q

List 4 causes of a high insulin:glucose ratio in hypoglycemia

A
  1. Exogenous insulin
  2. Sulfonyluria (ex. glyburide)
  3. Insulinoma
  4. Monogenic hyperinsulinism (ABCC8, KCNJ11, GCK, GLUD1)
  5. Dumping syndrome
  6. Autoimmune hypoglycemia
35
Q

List 6 causes of low insulin:glucose ratio in hypolgycemia

A
  1. Adrenal insufficiency
  2. GH deficiency
  3. Benign ketotic hypoglycemia
  4. Fatty acid oxidation defect
  5. Glycogen storage disease
  6. Sepsis
  7. Alcohol or other drugs (salicylate, beta blockers)
  8. Liver dysfunction
  9. Chronic renal insufficiency
  10. Starvation/malnourishment
36
Q

List 4 safety issues to counsel in a patient with hypoglycemia unawareness

A
  1. Driving: must be >5 to drive
  2. Alcohol: preventive measures to avoid hypoglycemia
  3. Exercise: adjust food or insulin for activity
  4. High-risk situations: avoid swimming alone
  5. Medic Alert bracelet
  6. Educate friends and family
  7. Always carry meter and source of rapid glucose/glucagon
37
Q

Name 3 genetic syndrome that can present with hyperinsulinism

A
  1. Beckwith-Wiedemann syndrome
  2. Sotos syndrome
  3. Kabuki syndrome
  4. Simpson-Golabi-Behmel syndrome

ENDOCRINOLOGY (21 decks)

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