• A 15-year-old high school student presents with sudden weight loss, increased urination and increased thirst.  He is an otherwise healthy individual who plays soccer on his schools team.  On physical exam you see a lean young man with dry mucous membranes.  Fingerstick glucose reveals a blood glucose of 469 mg/dL.
Insulin Overview  
  • Synthesis/Release  
    • synthesized as proinsulin in β cells of pancreas
      • proinsulin = insulin + C-peptide
      • C-peptide secreted with insulin 
      • detection in serum is a mechanism to determine origin of hyperinsulinemia
        • present with endogenous insulin, but absent with exogenous administration
    • hyperglycemia, GH, and cortisol ↑ insulin while hypoglycemia and somatostatin ↓ insulin secretion
    • β agonists ↑ release of insulin while α agonists ↓ insulin secretion
  • Function 
    • ↓ glucagon release by α cells of pancreas
    • ↑ Na+ retention (kidneys)
    • ↑ glycogen synthesis and storage
    • ↑ triglyceride synthesis and storage
      • recall babies of diabetic mothers are macrosomic
    • ↑ protein synthesis (muscles)
      • recall babies of diabetic mothers are macrosomic
    • ↑ cellular uptake of K+
      • recall used with glucose to treat hyperkalemia
    • ↑ glucose transport into skeletal muscle and adipose      
      • see Glucose transport topic
  • Pathology
    • a patient with an insulinoma will secrete abnormally high levels of insulin as well as C-peptide and will not produce anti-insulin antibodies
    • these patients will have severe hypoglycemia
Glucagon Overview
  • Production
    • secreted by the pancreas (alpha cells)
    • major stimulus for secretion is hypoglycemia
    • major inhibition of secretion in hyperglycemia
      • also inhibited by insulin and somatostatin
  • Function 
    • increase blood glucose
      • glycogenolysis
      • gluconeogenesis
      • inhibition of insulin release
    • increase blood levels of other energy forms
      • lipolysis
      • ketone body production
  • Pathology
    • a glucogonoma is a tumor that secretes excess glucagon leading to hyperglycemia as well as the characteristic rash of necrolytic migratory erythema 

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