Endocrine/Metabolic

Question 1

How do you calculate corrected sodium in DKA?

Answer 1

Corrected Sodium = Measured sodium + 0.016 * (Serum glucose - 100)

Another correction factor of 2.4 mEq/L for each 100 mg/dL above 100 mg/dL glucose is used in some papers

Clinical decision-making should be done based on corrected sodium

Question 2

What medications can interfere with thyroid activity?

Answer 2

Glucocorticoids, antiepileptics, catecholamines including dopamine, amiodarone

Question 3

Symptoms of glycogen storage disease

Answer 3

Lethargy after prolonged fasting, hypoglycemia with lactic acidosis and ketosis, hepatomegaly, growth failure, seizure from hypoglycemia

Question 4

Categorization of inborn errors of metabolism

Answer 4

Protein - amino acid, organic acid, and urea cycle metabolism > get accumulation of precursor amino acids, ammonia in urea cycle defects (can’t be metabolized to urea)

Lipid/fatty acid oxidation disorders - abnormal beta-oxidation of fatty acids, hypoglycemia WITHOUT ketones because need fatty acid metabolism to make ketones, during a period of fasting when glycogen and gluconeogenesis are used to maintain serum glucose, need fats for gluconeogenesis; seizure, rhabdomyolysis, cardiomyopathy, liver dysfunction

Mitochondrial disorders - decreased ATP and intracellular acidosis, brain, skeletal muscle, cardiac muscle most affected, lactic acidosis with organ-specific findings (stroke, seizure, cardiac conduction abnormalities, hypotonia, weakness

Question 5

Distinguish among different categories of inborn errors of protein metabolism

Answer 5

Amino acidemias
Organic adidemias
Urea cycle disorders

Only first two cause acidemia

Only later two cause hyperammonemia

Urea Cycle Defects:
Citrulline very elevated=citrullinemia
Citrulline a little elevated, argininosuccinic aciduria
No citrulline: carbamyl phosphate synthetase deficiency (no urine orotic acid) or OTC deficiency (high urine orotic acid)

Treatment IEM: Dextrose, no protein, maybe IV lipids; dialysis for severe hyperammonemia and lactatemia

Question 6

Risk factors for cerebral edema in DKA?

Answer 6

NOT fluid rate, rate of change of glucose, sodium content of rehydration fluid

What does matter:
- Lower initial CO2
- Higher initial BUN
- Sodium bicarb administration

Question 7

Causes of neonatal hypercalcemia

Answer 7

Maternal hypercalcemia
Subcutaneous fat necrosis
Primary hyperparathyroidism
Familial hypocalciuric hypercalcemia (parathyroid not sensitive to Ca)
Iatrogenic
Williams syndrome

Vitamin D deficiency can cause secondary hyperparathyroidism, but 1,25-dihydroxyvitamin D wouldn’t distinguish between primary and secondary hyperparathyroidism (normal or low Ca)

PTH stimulated by: low Ca, low Phos, low 1,25-vitaD

PTH goes to bone: release both Phos and Ca, osteoclast activity for bone turnover
PTH goes to kidney: absorb Ca, pee out Phos
»Net decrease in serum phos

Secondary hyperPTH: kidney disease, parathyroid overly responsive to low serum calcium

Tertiary hyperPTH: ESRD after renal transplant, parathyroid fails to respond normally to Ca signal