Master the board step 3

Master the Boards: USMLE Step 3
Diuretics are not used if
hydration increases urine
output.
Acute, Severe Hypercalcemia
This condition presents with the following:
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Confusion
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Constipation
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Polyuria and polydipsia from nephrogenic diabetes insipidus
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Short QT syndrome on the EKG
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Renal insufficiency, ATN, kidney stone
Treatment
1. Hydration: High volume (3–4 liters) of normal saline
2. Bisphosphonate (pamidronate) is very potent but slow, taking a week to
work. It inhibits osteoclasts.
3. Furosemide: Only after hydration has been given. Loop diuretics increase
calcium excretion by the kidney if urine is not being produced through
hydration alone.
4. Calcitonin: If hydration and furosemide do not control the calcium and
you need something faster than a bisphosphonate, then calcitonin is the
answer.
5. Steroid: Use if the etiology is granulomatous disease.
Basic Science Correlate
Mechanism of Volume Depletion in Hypercalcemia
High calcium levels inhibit the effect of ADH on the collecting duct, inducing
nephrogenic diabetes insipidus. High calcium filtration also promotes
osmotic diuresis.
Hypocalcemia
Hypocalcemia may be caused by the following:
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Surgical removal of parathyroid glands
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Hypomagnesemia: Magnesium is needed to release PTH from the gland.
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Vitamin D deficiency
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Acute hyperphosphatemia: Phosphate binds with the calcium and lowers it.
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Fat malabsorption: This binds calcium in the gut.
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PTH resistance: Pseudohypoparathyroidism that accompanies short fourth
finger, round face, and mental retardation
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