RESUMEN
Sixteen neonates, ranging in gestational age from 27 to 41 weeks and in postnatal age from birth to 8 days, were evaluated for their renal response to an endogenous PTH stimulus in 22 separate experiments. The PTH stimulus was generated by the decreased serum ionized Ca that accompanies exchange transfusion with citrated blood. The neonates increased their serum PTH from 95.8 +/- 13.1 to 133.9 +/- 15.4 microliterEq/ml (mean +/- SEM) during the transfusion, while increasing their urinary cAMP from 0.77 +/- 0.11 to 1.45 +/- 0.22 nmol/ml, and their urinary P from 12.9 +/- 2.6 to 30.6 +/- 6.1 mg/dl in the four hours following the exchange transfusion. This response was not related to postnatal or gestational age. We speculate that lack of renal responsiveness to PTH does not play a major role in the pathogenesis of early neonatal hypocalcemia.
Asunto(s)
Citratos/farmacología , AMP Cíclico/orina , Hipocalcemia/fisiopatología , Enfermedades del Recién Nacido/fisiopatología , Glándulas Paratiroides/efectos de los fármacos , Fosfatos/orina , Recambio Total de Sangre , Femenino , Humanos , Recién Nacido , Iones , Masculino , Hormona Paratiroidea/sangre , Hormona Paratiroidea/fisiología , Estimulación QuímicaRESUMEN
To determine the functional capabilities of the parathyroid glands, 17 EDTA infusions were given to 11 children (ages 1 month to 12 years) and to two mothers of four of the children. Serum ionized Ca fell from 4.1 mg/dl to 3.4 mg/dl. Excessive parathyroid hormone responses were elicited during seven of nine EDTA infusions in five children and in one adult with hypophosphatemic rickets, during the active phase of rickets. In four of five subjects with problems related to hypercalcemia, borderline low or undetectable PTH responses were elicited. Three relatively normal PTH responses were obtained, two in an infant after phosphate-induced hypocalcemic tetany was corrected, and one in a child with a malabsorption syndrome. The renal tubular reabsorption of phosphate was inversely related and the urinary cyclic AMP excretion was positively related to the PTH response. Thus EDTA infusions in infants and children might be useful in the identification of hyper-, normo-, or hypoparathyroid states and would be of value in defining the functional condition of the parathyroid glands in children with deranged Ca or P metabolism.