Recent advances in calcium metabolism. II. Disorders of calcium homeostasis

Growth hormone therapy in a poorly growing child with hypophosphatemic rickets

We treated a 10 6/12 year old prepubertal male with hypophosphatemic rickets, who was growing poorly despite appropriate treatment with calcitriol and phosphate, with exogenous growth hormone (for an initial trial period of 4 months, followed by 14 months of continuous treatment at a dose of 4 IU three times weekly) even though his growth hormone testing proved to be normal. His growth rate increased significantly during treatment with synthetic growth hormone (from a basal rate of 3.9 cm/yr to 9 cm/yr during the first 4 months of therapy and from 2.7 cm/yr to 6.0 cm/yr during next 14 months of treatment) and his predicted adult height increased as well. Slight metabolic changes were detected in this patient during treatment, with an increase in serum phosphorus and a decrease in twenty-four hour urine calcium concentrations. It would seem reasonable to evaluate the growth hormone status of children with hypophosphatemic rickets who are growing poorly despite appropriate therapy with calcitriol and phosphate and to consider a trial period of therapy with growth hormone in some of them.

Plasma thyrocalcitonin and parathyroid hormone concentrations in early neonatal hypocalcaemia

During the first week of life serum calcium, phosphorus, magnesium, immunoreactive thyrocalcitonin hormone, and parathyroid hormone concentrations were determined daily in 36 preterm and 29 small for gestational age, full term, healthy infants. Preterm babies with early neonatal hypocalcaemia had significantly higher concentrations of serum thyrocalcitonin hormone in the first four days of life than normocalcaemic preterm babies. Parathyroid hormone concentrations were similar in hypocalcaemic and normocalcaemic infants. In contrast, in the full term group no significant differences were detected in thyrocalcitonin hormone and parathyroid hormone patterns between hypocalcaemic and normocalcaemic subjects. This suggests two different pathogeneses for early hypocalcaemia in low birthweight infants. Hyperthyrocalcitoninaemia seems to be the main determining factor in preterm infants, while a non-hormonal pathogenesis should be considered in full term infants who are small for gestational age.

Calcium and phosphate metabolism in children with idiopathic hypoparathyroidism or pseudohypoparathyroidism: effects of 1,25-dihydroxyvitamin D3

Two children with congenital hypoparathyroidism and two children with pseudohypoparathyroidism were given maintenance doses of 15 to 45 ng/kg/day 1,25-dihydroxyvitamin D3 for a total of 255 months. The urinary calcium excretion showed an upward elevation after the first 2 years of treatment but was not significantly higher than that in 10 normal control subjects. The renal threshold for phosphate excretion stayed within the normal ranges compared with control values. Two hypercalcemic and two hypocalcemic episodes occurred during this period of treatment. Hypercalcemia was reversed within 1 week after withdrawal of 1,25-dihydroxyvitamin D3. Hypocalcemia was countered by increasing the dose of 1,25-dihydroxyvitamin D3. Renal functions were not adversely affected, as estimated by creatinine clearance and reciprocals of serum creatinine concentrations. The mean serum calcium concentration during 1,25-dihydroxyvitamin D3 treatment was significantly higher (P = 0.001) compared with that obtained during vitamin D2 treatment at a dose of 500 to 3000 IU/kg/day. These data provide additional support for the long-term use of 1,25-dihydroxyvitamin D3 in idiopathic hypoparathyroidism and pseudohypoparathyroidism.

Transient congenital hypoparathyroidism: possible association with anomalies of the pulmonary valve

Transient congenital hypoparathyroidism was observed in four neonates who also had congenital cardiac defects. Severe hypocalcemia and hyperphosphatemia were noted at 2 or 3 weeks of age, but resolved by 2 to 4 months of age with minimal treatment (oral calcium alone). Parathyroid hormone, measured with a highly sensitive, homologous antiserum, was initially borderline detectable and became easily detectable as the hypocalcemia resolved. Immune function was normal in each patient. The congenital cardiac defects in each case involved the pulmonary valve. These patients might be regarded as having either a partial form of the DiGeorge syndrome or a separate syndrome in which congenital pulmonary valve lesions are linked to delayed maturation of parathyroid function by an as yet obscure mechanism.

Rickets in premature infants receiving parenteral nutrition: a case report and review of the literature

There is a multifactorial etiology for rickets in premature infants receiving total parenteral nutrition. As an example of this, we describe a premature infant fed almost exclusively parenterally for the first 8 months of life who developed biochemical and radiologic evidence of rickets despite receiving vitamin D, calcium, and phosphorus at presently recommended levels. From our experience and a review of previous literature, there appears to be considerable uncertainty regarding the intravenous requirements of calcium, phosphorus, and vitamin D, particularly in low-birth weight infants. Therefore, measurements of serum 25-hydroxyvitamin D levels, vitamin D, and mineral intakes, and calcium and phosphorus excretion might be clinically useful for monitoring premature infants receiving total parenteral nutrition. Further research delineating more precisely the vitamin D, calcium, and phosphorus requirements of such infants is also suggested.

Common fluid and electrolyte problems in the pediatric intensive care unit

Administration of intravenous fluid to infants and children requires an understanding of the normal expenditure of water and electrolytes by the healthy child and the effects of specific illnesses on water and electrolyte turnover.

Rickets with alopecia: an inborn error of vitamin D metabolism

Rickets with alopecia, an inborn error of vitamin D metabolism, is described in two sisters. The rachitic disorder began during the first year of life and was refractory to 50,000 IU of vitamin D2/day. Surprisingly, both children had marked elevations in serum concentrations of 1,25-(OH)2D. Although the molecular basis for this disorder is not evident to date, intestinal end-organ unresponsiveness to exceedingly high levels of 1,25-(OH)2D was present, in addition to hyporesponsiveness of bone to these high levels of the hormone, since normocalcemia was maintained despite elevated serum levels of PTH. Therapy with oral 1,25-(OH)2D3 failed to reverse the disorder, but oral phosphorus supplements resulted in significant radiographic and clinical improvement.

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.

Reduction of serum-1, 25-dihydroxyvitamin-D3 in children receiving glucocorticoids

Serum-1,25-dihydroxyvitamin-D3 (1,25-[OH]2D3) was subnormal in children receiving long-term glucocorticoid treatment for various glomerular diseases, including nephrotic syndrome. In children with chronic glomerulonephritis not treated with glucocorticoids who had similar serum-creatinine with glucocorticoids who had similar serum-creatinine concentrations, serum-1,25-dihydroxyvitamin-D3 concentrations resembled those in healthy controls, indicating that glomerular renal disease per se does not account for reduced serum-1,25(OH)2DE concentrations in steroid-treated patients. The reduction in concentration of this most active vitamin-D metabolite correlated with the dose of steroid administered and with reduction in forearm bone mineral content measured by the photon absorption technique. Reduced serum-1,25-(OH)2D3 concentration may be important in the pathogenesis of steroid-induced osteopenia.

Parathyroid hormone and calcitonin secretion in uraemic infants

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.

Neonatal hypocalcaemia associated with maternal hyperparathyroidism. New pathogenetic observations

A 32-day-old male infant had hypocalcaemic convulsions associated with asymptomatic maternal hyperparathyroidism. Very low total and ionised serum calcium, increased serum phosphate, and normal serum parathyroid hormone (PTH) and 25-hydroxycholecalciferol (25-OHD3) concentrations were found at admission. After treatment with calcium and vitamin D, serum PTH and 25-OHD3 concentrations increased markedly before serum calcium levels returned to normal perhaps indicating an inability to convert 25-OHD3 to the metabolically active 1,25-dihyroxyvitamin D3 during the hyperphosphataemic state. Treatment with 1,25-dihdroxyvitamin D3 or its analogues is recommended.