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Abstract: PO1472

CYP24A1-Hypercalcemia in Pregnancy

Session Information

Category: Trainee Case Report

  • 902 Fluid, Electrolyte, and Acid-Base Disorders: Clinical


  • Shaikh, Sana J., Barnes-Jewish Hospital, Saint Louis, Missouri, United States
  • Vijayan, Anitha, Washington University in Saint Louis, Saint Louis, Missouri, United States

Hypercalcemia due to primary hyperparathyroidism and malignancy is common. However, rare genetic mutations in VitD metabolism (CYP24A1 & SLC34A1) are often culprits.

Case Description

33-year-old woman with chronic hypercalcemia, nephrocalcinosis, CKD 3, HTN was admitted at 34-weeks of gestation for symptomatic hypercalcemia (13.2 mg/dL). Labs showed ↓PTH (9 pg/mL), ↓/↔25-VitD (35 ng/mL) & ↑/↔1,25-VitD (65 pg/mL). Defect in VitD pathway was suspected. 25-VitD:24,25-VitD ratio returned raised (178). Genetic testing confirmed compound heterozygous CYP24A1 mutation.


CYP24A1 gene encodes 24-hydroxylase which inactivates 25-VitD and 1,25-VitD to 24,25-VitD and 1,24,25-Vit D. Biochemical profile includes ↑ serum & urinary calcium, ↓PTH, ↑25-VitD:24,25-VitD ratio +/- ↑ 1,25-VitD & 25-VitD. 25-VitD:24,25-VitD > 80 warrants genetic analysis.

Azoles inhibit 1-hydroxylase and ↓1,25-VitD, and can be utilized. Steroids ↓1,25-VitD production by activated macrophages, inhibit intestinal calcium absorption and induce CYP24A1, but this cohort is often resistant.

Pregnancy upregulates 1-hydroxylase, rendering patients with CYP24A1 mutations sensitive to hypercalcemia. Antepartum therapy options are limited. To limit adverse impact on maternal and fetal health, delivery may be required.

Maternal hypercalcemia with CYP24A1 mutations
ReferenceCYP24A1 MutationCommentsPharmacological
Shah AD et alCompound heterozygousGestational hypercalcemia x4-
Dinour D et alHomozygousGestational hypercalcemia x3 c/b exogenous VitD + Ca during third pregnancyD/c VitD + fluids, pamidronate, steroids
Kwong WT et alHomozygousGestational hypercalcemia x2Fluids, calcitonin
Woods GN et alHomozygousGestational hypercalcemia x2 c/b exogenous VitD + CaD/c VitD + fluids, calcitonin
Hedberg F et alCompound heterozygousSister I: gestational hypercalcemia x4 and postpartum hypercalcemia x1; sister II: gestational hypercalcemia x2Sister I: fluids, furosemide, calcitonin, pamidronate; Sister II: fluids
McBride L et alHomozygousGestational hypercalcemia x2Fluids, calcitonin, steroids
Arnold N et alCompound heterozygousGestational hypercalcemia c/b exogenous VitDFluids, furosemide, steroids during pregnancy + postpartum denosumab
Arnold N et alHomozygousPostpartum hypercalcemia in the third pregnancy c/b exogenous VitD + CaFluids, steroids, pamidronate, zoledronic acid, denosumab
Macdonald C et alCompound heterozygousGestational hypercalcemia in 1 of 2 pregnancies c/b exogenous VitDD/c VitD + short trial of steroids without response