Parathyroid hormone and calcitonin levels in vitamin D deficient rickets.

In six infants aged between 5 and 8 months with vitamin D deficient rickets, we have studied blood levels of calcium (Ca), phosphorus (P), alkaline phosphatase, immunoreactive parathyroid hormone (PTH) and calcitonin (CT), as well as urinary excretion of Ca, P, hydroxyproline and cyclic AMP, both under basal conditions and during a 4h infusion of 20 mg/kg 10% Ca gluconate in normal saline. Under basal conditions all the infants had high alkaline phosphatase (range: 470--770 U.I./1); PTH (range: 620--1200 pg Eq/ml) and CT (range: 440--750 pg/ml) but two infants had hypocalcaemia and four had normocalcaemia and hypophosphataemia. The urinary Ca excretion was low whereas the urinary P, hydroxyproline and cyclic AMP excretions were high. During Ca infusion the total serum Ca and CT levels increased, while alkaline phosphatase and PTH fell. After the end of the infusion, CT levels fell perceptibly; phosphaturia, hydroxyprolinuria and cyclic AMP decreased on the day of the infusion.