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Bone material / compositional properties are significant determinants of bone quality, thus strength. Raman spectroscopic analysis provides information on the quantity and quality of all three bone tissue components (mineral, organic matrix, and tissue water). The overwhelming majority of the published reports on the subject concern adults. We have previously reported on these properties in growing children and young adults, in the cancellous compartment. The purpose of the present study was to create normative reference data of bone material / compositional properties for children and young adults, in the cortical compartment. We performed Raman (Senterra (Bruker Optik GmbH), 50× objective, with an excitation of 785 nm (100 mW) and a lateral resolution of ~0.6 μm) microspectroscopic analysis of transiliac bone samples from 54 individuals between 1.5 and 23 years of age, with no known metabolic bone disease, and which have been previously used to establish histomorphometric, bone mineralization density distribution, and cancellous bone quality reference values. The bone quality indices that were determined were: mineral/matrix ratio (MM) from the integrated areas of the v

Short-term skeletal changes in children with newly diagnosed glucocorticoid-treated nephrotic syndrome J. Feber, J. Roth, P.M. Miettunen, A. Ni, N. Alos, S. Atkinson, R. Stein, R. Couch, E. Cummings, F.H. Glorieux, J. Hay, B. Lentle,M.Matzinger, H. Nadel, F. Rauch, C. Rodd, D. Stephure, S. Taback, N. Shenouda, K. Siminoski, L.M. Ward, the Canadian STOPP Consortium University of Ottawa, Ottawa, ON, Canada University of Calgary, Calgary, AB, Canada Children's Hospital of Eastern Ontario, Ottawa, ON, Canada Universite de Montreal, Montreal, QC, Canada McMaster University, Hamilton, ON, Canada University of Western Ontario, London, ON, Canada University of Alberta, Edmonton, AB, Canada Dalhousie University, Halifax, NS, Canada McGill University, Montreal, QC, Canada Brock University, St. Catharines, ON, Canada University of British Columbia, Vancouver, BC, Canada University of Manitoba, Winnipeg, MB, Canada Canadian Pediatric Bone Health Working Group, Ottawa, ON, Canada

Hypocalcemia is commonly observed in the neonatal period and is usually transient from a few days to a few weeks. On only rare occasions is neonatal hypocalcemia permanent and secondary to congenital hypoparathyroidism caused by either isolated absence of parathyroid glands or in association with other malformations. Most cases of neonatal hypocalcemia fall into one of two clinical categories. Namely early neonatal hypocalcemia occurs in 24–48 h of life and it is usually observed in premature infants or infants of diabetic mothers. Late neonatal hypocalcemia is observed at the end of the first week of life. In addition of these two major categories, neonatal hypocalcemia may occur in association with hypomagnesemia.

To assess the relationship between maternal and fetal mineral homeostasis, serum calcium, magnesium, inorganic phosphate, parathyroid hormone, and vitamin D metabolite concentrations in venous cord sera from 15 preterm singletons and 3 twin pairs were compared with the levels found in maternal sera. Cord calcium, magnesium, and phosphorus levels were significantly higher than the respective levels in maternal samples. There was a significant relationship between the two compartments for all three analyses. Cord serum 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D levels were significantly lower than those observed for the mothers. Association of the cord concentration with that of the mothers was observed only for the first two metabolites. There was no relationship between the maternal 1,25-dihydroxyvitamin D levels and gestational age, calcium, magnesium, inorganic phosphate, or 25-hydroxyvitamin D. Cord 1,25-dihydroxyvitamin D correlated significantly only with cord calcium levels. Immunoreactive parathyroid hormone levels were within normal limits both in cord and maternal samples. Our data suggest that after 31 weeks of gestation: (1) calcium, magnesium, and inorganic phosphate cross the placental barrier against a concentration gradient; (2) the fetus depends on the maternal supply for 25-hydroxyvitamin D and 24,25 dihydroxyvitamin D; (3) the feto-placental unit synthesizes 1,25-dihydroxyvitamin D according to fetal needs.

Decrease in serum calcium level leading to hypocalcemia during the first week of life is a frequent finding in premature neonates. Eight premature neonates presenting with such an episode of hypocalcemia in the course of their first 4 days of life were studied. They were fed with a phosphate-enriched human milk and given vitamin D3 (2,100 IU/day per os). We have evaluated the effect of a 24-hour pharmacologic calcium infusion on the circulating levels of calcium, inorganic phosphate, magnesium, 25-hydroxycalciferol (25-OHD), 1α,25-dihydroxycalciferol [1,25(OH)2D] and immunoreactive parathyroid hormone (iPTH). After the infusion, circulating iPTH and Pi levels dropped significantly (p < 0.025 and p < 0.005 respectively) whereas serum Ca and 25-OHD (p < 0.005) increased. Mg and 1,25(OH)2D serum levels remained unchanged. Our data show that an increased calcium supply sustained for 24 h induces an appropriate response in iPTH secretion. Effects on circulating levels of 1,25(OH)2D were variable and probably reflected individual differences in half life of 1,25(OH)2D or in set points in the feedback mechanisms involved in the control of 1,25(OH)2D synthesis.

Perinatal metabolism of vitamin D was studied in premature babies with the aim of: (1) reporting the relationship between the pregnant mother and her preterm infant and the metabolism of vitamin D during the first weeks of life, and (2) assessing the effect of vitamin D metabolites on phosphorus calcium and magnesium intestinal absorption. There was only a positive correlation between plasma cord calcium and 25-hydroxyvitamin D levels and the mother’s plasma levels at birth. During the hypocalcemic episode observed during the first week of life, vitamin D activation did occur, but later on rickets or osteomalacia cannot be due to the low levels of vitamin D metabolites in the preterm receiving an adequate dose of vitamin D (1,000–1,200 IU of D2). Calcitriol, the major metabolite of vitamin D, is acting on the intestine and promotes calcium absorption even in very tiny prematures. The pathogenesis of hypomineralization in the preterm infant is due to the low intake of calcium or phosphorus and/or poor absorption of calcium in the case of vitamin D deficiency.