Learn / Metabolism / The test
Metabolic reasoning
Whole-map thinking. Each case is a chain of cause → effect that ends in the labs: why DKA has ketones and hyperglycemia, why a drinker goes hypoglycemic, why an infant with MCAD deficiency spills no ketones. Walk through the chain on the map, then order it yourself, answer the why questions, or diagnose from the labs.
A toddler with a huge liver and seizures before breakfast
A 9-month-old has had several early-morning seizures. He has a protuberant abdomen with marked hepatomegaly, doll-like facies and poor growth. Symptoms appeared as feeding intervals lengthened.
| Fasting glucose | 35 mg/dL | ↓↓ |
| Lactate | ↑↑ | ↑ |
| Uric acid | ↑ | ↑ |
| Triglycerides | ↑↑ | ↑ |
| Ketones | ↑ | ↑ |
| Response to glucagon | no rise in glucose; lactate rises | abnormal |
Von Gierke disease (glycogen storage disease type Ia)
Glucose-6-phosphatase is the final shared step of glycogenolysis AND gluconeogenesis — lose it and the liver cannot release glucose by any route.
Condition card: Von Gierke disease (GSD type I; secondary hyperuricemia) →Pathway map →
- Between feeds, glucagon activates glycogen phosphorylase → glycogen → glucose-1-P → glucose-6-P — this part works.
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Pathways involved: Glycogen synthesis & breakdown, Gluconeogenesis, HMP shunt (pentose phosphate pathway). Drill them one at a time in Metabolic pathways.