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

Background: Hyperparathyroidism occurs rarely in pregnancy; this is the fir st reported case in a twin gestation. Management of this unusual case is de scribed and an overview of fetal/maternal calcium homeostasis is discussed. Methods: The patient presented at 33 weeks' gestation with hypertension an d premature labor. Serum calcium and phosphorus were 14.6 and 1.7 mg/dL, re spectively. 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. Alt hough the calcium remained elevated between 12.6 and 13.3 mg/dL, medical th erapy was continued because of the risks of surgery in the third trimester. Alternative medical treatments (bisphosphonates, calcitonin) were consider ed ill advised in pregnancy. The patient remained asymptomatic without furt her labor, and at week37, fraternal twins were delivered by cesarean sectio n. The infants were monitored closely and experienced no hypocalcemic sympt oms after delivery. Postpartum, the mother's parathyroid scan and ultrasoun d were negative. She underwent neck exploration and a single 700-mg adenoma was removed. Transient asymptomatic hypocalcemia (7.5 mg/dL) occurred post operatively, and she was placed on oral calcium (1500 mg/day) and calcitrio l (0.25 mg/day). These were stopped at 8 weeks, when both PTH and parathyro id hormone-related peptide levels were normal. Conclusion: Mother and infan ts continue to do well after 18 months. This case provides an interesting s etting to consider the interrelationships between elevated maternal PTH and the fetal/placental factors that regulate calcium metabolism in pregnancy.