Parathormone and perinatal calcium homeostasis.

Plasma parathormone (PTH) and calcium concentrations were measured in 309 specimens collected from 190 newborns during the first 7 days of life. The patient material consisted of 51 preterm, 130 term, and 9 postterm infants, including 22 infants of diabetic mothers (IDM), 38 infants with hypocalcemia, and 25 asphyxiated infants. PTH was detectable, although in low concentrations, in cord blood samples despite the presence of elevated calcium concentrations. Postpartum, PTH concentrations in term, appropriate for gestational age (AGA) infants remained low during the first 2 days of life; a significant (P less than 0.05) and sustained increase in plasma hormone levels was noted starting on day 3. PTH concentrations in IDM and preterm infants remained low for 3 days and a significant hormone increase did not occur until day 4. Hypocalcemia was common in IDM and asphyxiated infants; these infants accounted for two-thirds of all hypocalcemic infants. The profile of plasma calcium in IDM during the first week of life was different than that of any other group of infants. Plasma calcium concentrations remained depressed over this period of time and exhibited a temporary drop on day 4 accompanied by an increase in plasma PTH levels. Asphyxiated infants exhibited low plasma calcium concentrations, despite PTH levels that were significantly (P less than 0.007) higher than those of age-matched term AGA newborns.