Parathyroid hormone and calcitonin secretion in uraemic infants

Abstract

In six infants aged between 4 and 8 months with chronic renal failure, 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 under basal conditions and during an infusion of 20 mg/kg of 10% Ca gluconate in normal saline over 4 h. Under basal conditions four infants had normal serum Ca and P values, alkaline phosphatase levels at the upper limit of normal, and very high PTH (range: 1450--2550 pg Eq/ml) and CT (range: 700--1900 pg/ml) levels. The urinary Ca excretion was low, whereas the urinary excretion of P, hydroxyproline and cyclic AMP was high. During Ca infusion, the total serum Ca and CT levels increased, PTH fell without however reaching the normal upper limit, and urinary P and cyclic AMP excretion decreased. In two infants with osteodystrophy and the highest levels of PTH (2900 and 3500 pg Eq/ml respectively) there was no suppression of PTH during Ca infusion.

Parathyroid hormone and calcitonin levels in vitamin D deficient rickets

“…These two parameters are also altered in the early stage of rickets, but they seem to be directly related to the gravity and duration of the illness and to the levels of PTH. We found the highest values in infants 3, 4, 5, and 6--the levels of hydroxyproline were comparable to values reported by us in uraemic infants with osteodystrophy [27]. The increase of alkaline phosphatase and urinary excretion of hydroxyproline in vitamin-D deficient rickets was probably also due to stimulation of osteolysis by PTH [16, …”

“…Moreover, it is well known that PTH contributes to the urinary excretion of cyclic AMP and that high levels of urinary cyclic AMP have been found in hyperparathyroidism [15]. In our previous paper we reported [27] increased urinary excretion of cyclic AMP in uraemic infants with secondary hyperparathyroidism. Calcium infusion reduced the excretion of cyclic AMP, probably by inhibiting parathyroid function, although a direct effect of calcium on renal adenyl cyclase cannot be excluded [24].…”