hyporglycemia

Question 1

Definition of hypoglycemia

Answer 1

plasma glucose low enough to cause signs or symptoms –> impairment of brain function
Typically <70 mg/dl

Whipples triad- symptoms/signs consistent with hypoglycemia, low measured plasma glucose concentration, resolution of symptoms/signs with increasing plasma glucose

Question 2

Physiologic defenses against hypoglycemia

Answer 2

brain relies on glucose as fuel, many physiological adaptations to prevet hypoglycemia,

Initially, defense is a decrease in insulin secretion, followed by an increase in glucagon

Glucagon acts on the liver by stimulating glycogenolysis and gluconeogenesis

Increase in epinephrine, increases delivery of substrates for gluconeogenesis and inhibits glucose utilization by several tissues and inhibits insulin secretion

Question 3

Counter regulatory hormone response to hypoglycemia

Answer 3

insulin from the pancreas, decreases secretion of insulin

glucagon from liver, glycogenolysis, gluconeogenesis

Epinephrine Beta 2 adrenergic- increase substrate for gluconeogenesis, alpha 2 receptors inhibit insulin secretion

Cortisol and growth hormone- if hypoglycemia persists- limit glucose utilization, enhance gluconeogenesis

Question 4

Signs and symptoms of hypoglycemia

Answer 4

Neurogenic (autonomic)- tremor, palpitations, anxiety/arousal, sweating, hunger, others

Neuroglycopenic- cognitive impairment, behavioral changes, psychomotor abnormalities, visual changes, seizures, coma

Question 5

causes of hypoglycemia

Answer 5

insulin, liver jidney etc Cortisol, insulinoma, nesidoblastosis, post bypass, insulin autoimmune antibody to insulin

Question 6

insulinoma

Answer 6

insulin secreting tumors (neuroendocrine) of pancreatic origin that cause hypoglycemia, rareish, usually benign, evenly distributed thru the pancrease, diagnosis made per hormonal studies when hypoglycemic

Question 7

Supervised fast

Answer 7

provokes hormonal responses that maintain euglycemia, symptomatic hypoglycemia, should not normally occur during a prolonged fat given ongoing gluconeogenesis, a supervised fast for up to 72 hours can be used to determine the presence and etiology of hypoglycemia

Endpoints for the test- plasma glucose <45 mg/dl, signs and symptoms of hypoglycemia, >72 hours have elapsed, plasma glucose<55

measure c peptide– endogenous marker of insulin

Insulin should go down

Question 8

mixed meal test

Answer 8

not standardized and validated like the 72 hour fast

Used to evaluate patients with postprandial symptoms

measure plasma glucose, proinsulin, insulin, and c peptide premeal (fasting) then every 30 mins post meal (mixture fats carbs and protein)

trying to confirm if hypoglycemia is the cause of the symptoms and whether this is insulin mediated

helpful in pts with post prandial symptoms (roux-en y g bypass)