Decline in serum calcium, magnesium, and phosphorus values with oral glucose in normal neonates: studies of serum parathyroid hormone and calcitonin.

In 10 normal term infants aged 52 +/- 2.5 hours, serum calcium, magnesium, phosphorus, ionized calcium, parathyroid hormone, and calcitonin were studied at 0, 1/2, 1, and 2 hours after administration of 1.77 +/- 0.08 gm/kg glucose orally over 20 minutes. In response to glucose administration, serum glucose concentration rose and serum P, Ca, and Mg concentrations fell. Serum PTH concentration rose significantly, and blood ionized Ca and pH were unaltered. Serum calcitonin was elevated, as compared with adult values, and did not change. We suggest that in neonates, as in adults, oral ingestion of glucose lowers serum Ca, Mg, and P, and a compensatory rise in serum PTH concentration maintains blood ionized Ca concentration.