Calcium, magnesium, phosphorous Flashcards
how much of the calcium distribution is extracellular? how much of that is free? bound?
- 1% is extracellular (50% free, 50% bound)
what is the relationship between albumin and calcium?
for every 1g / dL drop in serum albumin below 4 g / dL, measured serum calcium decreases by 0.8 mg /dL
when you see that calcium is low, what should you think about?
albumin levels
what are the calcium regulatory hormones?
- PTH
- calcitonin
- vitamin D
what are the roles of PTH? what is the net effect?
- increase osteoclastic bone resorption of calcium and phosphate
- increase DCT calcium reabsorption
- decreases PCT phosphate reabosorption
- increases gut absorption of calcium
NET EFFECT: increased serum calcium and decreased serum phosphate
what are the roles of calcitonin? what is the net effect?
- inhibits osteoclastic bone resorption
- decreases renal tubular reabsorption of calcium and phosphate
- decreases gut absorption of phosphate
NET EFFECT: decreased serum calcium and phosphate
what are the roles of vitamin D? what is the net effect?
- increase intestinal absorption of calcium and phosphate
- increase bone resorption of calcium and phosphate by increasing osteoclast activity
- increase renal reabsorption of calcium and phosphate
- decrease production of PTH
NET EFFECT: increased serum calcium and phosphate
what are the signs and symptoms for hypercalcemia?
- CNS
- neuromuscular
- CV
- renal
- GI
- metastatic calcification?
- CNS: lethargy, psychosis, coma
- neuromuscular: myalgias, weakness
- CV: bradycardia, short QT
- renal: polyuria, decreased GFR, nephrolithiasis, nephrocalcinosis
- GI: anorexia, nausea, constipation
- metastatic calcification: yes
what does hypocalcemia do to the QT interval?
prolongs
what are the ddx for hypercalcemia?
- primary hyperparathyroidism
- malignancy
- drug induced
- granulomatous disease / immobilization / acidosis
what drugs / medications can cause hypercalcemia?
- vitamin A
- vitamin D
- thiazide diuretics
- lithium
- milk-alkali
how do thiazide diuretics cause drug induced hypercalcemia?
increased renal reabsorption of calcium
how does lithium cause drug induced hypercalcemia?
- failure of suppression of PTH secretion by calcium
- hypocalciuria
what are the treatment options for hypercalcemia?
- ECF volume restoration
- loop diuretics
- bisphosphonates
- calcitonin
- glucocorticoids
- dialysis
what are the mild / moderate / severe levels for hypocalcemia?
- mild: 8.0-8.5
- moderate: 7.0-7.5
- severe: under 7.0
what are the signs and symptoms of hyocalcemia?
- paresthesias
- tetany
- long QT, arrhythmias
- seizures
vitamin D dependent rickets type 1 is due to a deficiency in what enzyme?
1-alphahydroxylase
vitamin D dependent rickets type 2 is due to a mutation in what receptor?
vitamin D receptor
what are the roles of phosphorous?
- structural component of most biological membranes
- nucleotides and nucleic acids
- signal transduction
- temporary storage and transfer of the energy derived from metabolic fuel
- enzyme regulation: activation of many catalytic proteins by phosphorylation
what are the symptoms of hyperphosphatemia?
- hypocalcemia-related: muscle spasms, perioral numbness
- related to underlying condition: fatigue, SOB, edema, lack of appetite, N/V
what are the etiologies of hyperphosphatemia?
- acute phosphate load
- increased tubular reabsorption of phosphate
what are the symptoms of severe hypophosphatemia?
- weakness
- bone pain
- rhabdomyolysis
- mental status changes
what are the etiologies of hypophosphatemia?
- inhibition of distal tubular reabsorption of calcium and magnesium (hypercalciuria)
- intracellular phosphate depletion
what are the hematological effects of hypophosphatemia?
- RBCs: hemolysis, RBC rigidity
- WBCs: decreased phagocytosis and chemotaxis
- platelets: defective clot retraction, thrombocytopenia
what conditions are associated with symptomatic hypophosphatemia?
- chronic alcoholism
- refeeding syndrome
- chronic ingestion of antacids
what is the most common cause of hyperphosphatemia? why is this?
- renal failure
- urinary excretion cannot balance phosphate intake
what are the roles of magnesium?
- enzyme cofactor
- required for oxidative phosphorylation
- bone development
- DNA, RNA synthesis
- transport of calcium and potassium across cell membranes
what are the symptoms of hypomagnesemia?
- nystagmus
- fatigue
- seizures
- muscle spasms
- weakness: diaphragm
- numbness
what does hypomagnesemia do to the QT interval?
prolongs
