Endocrinology

Hypoglycemia - Causes & Mechanisms song

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Hypoglycemia - Causes & Mechanisms

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Insulinoma causes fasting hypoglycemia with elevated insulin, elevated C-peptide, and elevated proinsulin — C-peptide distinguishes it from exogenous insulin injection, where C-peptide is suppressed.
Exogenous insulin overdose presents with high insulin levels but low C-peptide, because injected insulin does not contain C-peptide.
Sulfonylureas stimulate pancreatic beta cells to release insulin independent of glucose, causing hypoglycemia with elevated insulin AND elevated C-peptide — distinguishable from insulinoma only by sulfonylurea screen.
Reactive hypoglycemia occurs 2–4 hours postprandially due to excessive insulin release, commonly seen after gastric bypass surgery (dumping syndrome).
Cortisol and glucagon are the primary counter-regulatory hormones; deficiency in either — as seen in Addison disease or glucagonoma resection — impairs recovery from hypoglycemia.
Von Gierke disease (glucose-6-phosphatase deficiency) causes fasting hypoglycemia because the liver cannot release free glucose from glycogen or gluconeogenesis.
In alcohol-induced hypoglycemia, excess NADH from ethanol metabolism inhibits gluconeogenesis by depleting oxaloacetate, causing fasting hypoglycemia after binge drinking without food intake.
IGF-2-secreting tumors (non-islet cell tumor hypoglycemia) cause hypoglycemia with low insulin and low C-peptide, as IGF-2 activates insulin receptors directly.
Factitious hypoglycemia from surreptitious sulfonylurea use is identified by urine or serum sulfonylurea screen, not insulin or C-peptide levels alone.
Neonatal hypoglycemia in infants of diabetic mothers results from fetal hyperinsulinism driven by chronic maternal hyperglycemia causing beta-cell hypertrophy in utero.