276 IMPAIRED NEONATAL PARATHYROID FUNCTION AND MATERNAL HYPERPARATHYROIDISM

Abstract

Hypocalcemia (serum Ca 6.5 mg/100 ml) and hyperphosphatemia (serum P 9.5 mg/100 ml) were observed in a 10-day-old female infant with increased neuromuscular irritability. Hypocalcemia persisted until the sixth week of life and was resistant to conventional therapy. During this period the serum P remained elevated and the serum Mg was low normal to mildly depressed. In the presence of hypocalcemia, circulating immunoreactive parathyroid hormone (iPTH) levels in the neonate were inappropriately low. In contrast to the newborn infant, the asymptomatic mother was hypercalcemic (serum Ca 11.7-12.3 mg/100 ml), hypophosphatemic (serum P 1.5-2.1 mg/100 ml) and had consistently elevated circulating iPTH levels. Subsequently, an adenoma was removed from the left superior parathyroid gland of the mother and her serum Ca and iPTH levels returned to normal. This study indicates that parathyroid function was depressed in a hypocalcemic infant born of an asymptomatic hyperparathyroid mother. This finding is consistent with the hypothesis that in maternal hyperparathyroidism an increase in maternal circulating Ca and/or parathyroid hormone facilitates Ca transport across the placenta, leading to fetal hypercalcemia which, in turn, suppresses parathyroid activity in the fetus and neonate and thereby promotes the development of hypocalcemia in the newborn period.