Hypercalcemic Crisis in Pregnancy

PHPT associated with pregnancy is a rare condition.33"35 Although the exact incidence of PHPT during pregnancy is unknown, the incidence of PHPT in women of childbearing age is estimated to be approximately 8 cases per 100,000 population per year.36

Maternal PTH levels increase to enhance gastrointestinal absorption of calcium during pregnancy,37 thereby facilitating placental transport of calcium to the fetus. The degree of hypercalcemia, however, may be blunted by the physiologic hypoalbuminemia of pregnancy. Some of the criteria used to make the diagnosis of hyperparathyroidism in nonpregnant patients should be adjusted (i.e., lower calcium and higher PTH levels should be used) because of the physiologic increase in maternal PTH levels associated with pregnancy and the normally depressed maternal calcium levels.

The maternal hypercalcemia accompanying maternal HPT depresses fetal parathyroid function.37 After birth, the neonate no longer has access to maternal serum calcium and is unable to mobilize calcium adequately from bone because of depressed parathyroid function, resulting in a risk of neonatal tetany. The pregnant woman, in turn, is at risk for hypercalcemic crisis. Placental delivery of calcium to the fetus is greatest during the third trimester and is protective for the mother.33,38 Because this protection is lost with the delivery of the child, the neonate is at greatest risk for tetany several hours after delivery, and the mother is at greatest risk for hypercalcemic crisis during the same period.37,39

The incidence of fetal complications has been reported to be 53% for treated mothers35,40 and 80% for untreated mothers,40 27% to 31% of whose infants die in the neonatal period.35,40 Other complications include intrauterine growth restriction, low birth weight, preterm delivery, and intrauterine fetal demise.33,35,40"42 Postpartum neonatal hypocalcemic tetany has been reported to occur in 50% of infants born to untreated mothers.6 The diagnosis of HPT in pregnant patients is most commonly made postpartum when the infant develops neonatal tetany.37

If hypercalcemia is not controlled medically, parathyroidectomy by an experienced surgeon should be recommended despite advanced gestation.39 Urgent parathyroidectomy using improved technology is the best option, even in late gestation. Developments in surgical technology have greatly improved the safety of parathyroidectomy.43"45 Innovations such as the intraoperative quick PTH assay,28 ses-tamibi scintigraphy,46,47 and radioguided parathyroidectomy48 have allowed the development of minimally invasive parathyroidectomy, and several investigators have reported high success rates using these techniques, with reductions in incision length, operation time, and length of hospital stay in nonpregnant patients with PHPT.4M5-49 These methods may not be used in pregnant women, but they offer the theoretical advantage of maximizing surgical efficacy while minimizing invasiveness and operation time.50,51 An alternative option is medical control, such as with bisphosphonates and calcitonin. The diagnosis and management of this condition are imperative because it poses a significant risk to the mother as well as the fetus.

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