Primary hyperparathyroidism in a twin pregnancy and review of fetal/maternal calcium homeostasis

Background: Hyperparathyroidism occurs rarely in pregnancy; this is the first reported case in a twin gestation. Management of this unusual case is described and an overview of fetal/maternal calcium homeostasis is discussed. Methods: The patient presented at 33 weeks' gestation with hypertension and premature labor. Serum calcium and phosphorus were 14.6 and 1.7 mg/dL, respectively. An intact parathyroid hormone (PTH) level was 243 pg/mL (normal, 10-65). Results: The patient was treated with parenteral saline hydration and oral phosphate supplementation that was continued through week 37. Although the calcium remained elevated between 12.6 and 13.3 mg/dL, medical therapy was continued because of the risks of surgery in the third trimester. Alternative medical treatments (bisphosphonates, calcitonin) were considered ill advised in pregnancy. The patient remained asymptomatic without further labor, and at week37, fraternal twins were delivered by cesarean section. The infants were monitored closely and experienced no hypocalcemic symptoms after delivery. Postpartum, the mother's parathyroid scan and ultrasound were negative. She underwent neck exploration and a single 700-mg adenoma was removed. Transient asymptomatic hypocalcemia (7.5 mg/dL) occurred postoperatively, and she was placed on oral calcium (1500 mg/day) and calcitriol (0.25 mg/day). These were stopped at 8 weeks, when both PTH and parathyroid hormone-related peptide levels were normal. Conclusion: Mother and infants continue to do well after 18 months. This case provides an interesting setting to consider the interrelationships between elevated maternal PTH and the fetal/placental factors that regulate calcium metabolism in pregnancy.