Pathology Questions for the RDN Exam — Practice Free

Insulin is the primary driver. During starvation, the body is in a catabolic state (low insulin, high glucagon). Reintroduction of carbohydrates triggers insulin secretion, which stimulates the Na+/K+ ATPase pump and glucose uptake. This causes an abrupt shift of potassium, magnesium, and phosphate from the extracellular space into the cells. Resulting serum hypophosphatemia is the hallmark sign. Exam Tip: CDR often tests the shift from fat metabolism (ketones) back to carbohydrate metabolism (glucose) as the metabolic trigger.

Morning hyperglycemia in GDM is driven by increased insulin resistance due to the diurnal rhythm of cortisol and the surge of placental hormones (human placental lactogen) in the early morning hours. This decreases insulin sensitivity most significantly during the first meal of the day. Clinical Pearl: RDNs should recommend a breakfast low in carbohydrates (15-30g) and avoid fruit or fruit juices at breakfast, as these are rapidly absorbed and exacerbate the glucose spike during this period of peak resistance.

It increases the acid load (lowers urine pH) and increases urinary uric acid excretion. Rationale: Animal proteins are high in purines (precursors to uric acid) and sulfur-containing amino acids, which acidify the urine. Acidic urine (pH <5.5) promotes the conversion of soluble urate to insoluble uric acid crystals. Exam Strategy: Note that animal protein affects both calcium and uric acid stones by lowering pH and increasing calcium/uric acid excretion. Plant proteins have a more neutral/alkaline effect.

D-lactic acidosis. This occurs when malabsorbed carbohydrates reach the colon and are fermented by specific bacteria (e.g., Lactobacillus) into D-lactate. Unlike L-lactate, the human body cannot efficiently metabolize D-lactate, leading to systemic accumulation and neurological impairment. Management includes limiting simple sugars and potentially using oral antibiotics to alter colonic flora. Exam Tip: Standard lab tests for lactate only measure L-lactate; a specific D-lactate assay is required for diagnosis.

MNT: Small, frequent meals of dry, bland foods (crackers, toast); avoid strong odors; consume liquids between meals rather than with them. Ginger (0.5-1.0g/day) may be used as an adjunct. Avoid favorite foods during nausea to prevent learned food aversions. Exam Tip: Distinguish between acute CINV (<24 hours) and delayed CINV (>24 hours) for clinical timing of interventions.