Hypercalcemia

Calcium Metabolismmedium

A 34-year-old woman presents with 3 days of nausea, vomiting, and confusion. She recently adopted an 'organic' lifestyle and has been taking large doses of over-the-counter calcium carbonate and vitamin D supplements. She was previously healthy except for hypothyroidism treated with levothyroxine. Labs: calcium 13.6 mg/dL, creatinine 2.3 mg/dL (baseline 0.8), and an arterial blood gas showing metabolic alkalosis (HCO3- 34 mEq/L); phosphate is low-normal and intact PTH is suppressed. Pregnancy test is negative. Which of the following is the most likely diagnosis?

  1. A.Hyperemesis gravidarum with volume depletion
  2. B.Calcium-alkali (milk-alkali) syndromeCorrect
  3. C.Humoral hypercalcemia of malignancy
  4. D.Thyrotoxicosis-related hypercalcemia

Explanation

The triad of hypercalcemia, metabolic alkalosis, and acute kidney injury in a patient ingesting large amounts of calcium plus absorbable alkali (calcium carbonate) is the calcium-alkali (formerly milk-alkali) syndrome, now a leading cause of hospitalization for hypercalcemia because of widespread calcium and vitamin D supplement use. The suppressed PTH is consistent with an exogenous calcium load, and the negative pregnancy test excludes hyperemesis gravidarum. Hypercalcemia of malignancy is unlikely in a previously healthy young woman with a clear supplement history and typically presents without this degree of metabolic alkalosis. Thyrotoxicosis can rarely cause mild hypercalcemia but would not produce this alkalosis or AKI picture.

Why each option

A.
Excluded by the negative pregnancy test; hyperemesis is a pregnancy-specific condition.
B.
Correct. Hypercalcemia + metabolic alkalosis + AKI with suppressed PTH after high calcium/alkali intake defines calcium-alkali syndrome.
C.
Unlikely in a healthy young woman with a clear supplement history, and it does not typically cause this metabolic alkalosis.
D.
Thyrotoxicosis causes at most mild hypercalcemia and does not explain the alkalosis or AKI.

Reference: Patel AM, Goldfarb S. Got calcium? Welcome to the calcium-alkali syndrome. J Am Soc Nephrol. 2010;21(9):1440-1443.

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