Evidence for extrarenal production of 1,25-dihydroxyvitamin during physiological bone growth: in vivo and in vitro production by deer antler cells.

The development of deer antler follows a pattern similar to that described for mammalian endochondral ossification and has been proposed as a suitable model for studies of bone growth. We investigated seasonal changes in the plasma concentrations of 1,25-dihydroxyvitamin D [1,25-(OH)2D] and calcium and the activity of alkaline phosphatase in relation to the antler cycle during 1 yr in 4 captive roe deer and measured these biological parameters in 27 wild roe deer during their antler cycle. A significant elevation of 1,25-(OH)2D in peripheral plasma, with no parallel increase in the concentration of its precursor 25-hydroxyvitamin D, was observed to accompany the rapid growth phase of the antler cycle in captive (P less than 0.001) and wild (P less than 0.025) deer. During the same phase there was a gradient in levels of 1,25-(OH)2D in antler vs. jugular blood (P less than 0.01). In addition, velvet cells in culture proved to have the ability to convert 25-hydroxyvitamin D3 into a more polar derivative, which was indistinguishable from true 1,25-(OH)2D3 with regard to its chromatographic properties, its UV absorbance at 254 nm, and its ability to bind to the 1,25-(OH)2D3 receptors present in chick intestinal cytosol. These in vivo and in vitro results strongly suggest that local production of 1,25-(OH)2D by the antler cells does occur in vivo and may contribute to the increase in plasma 1,25-(OH)2D during bone growth.

Effects of long-term maintenance therapy with a new glucocorticoid, deflazacort, on mineral metabolism and statural growth.

Deflazacort was substituted for Prednisone (based on the equivalence 1 mg Prednisone equals 1.2 mg Deflazacort), during maintenance glucocorticoid therapy in 9 children, 5 with renal diseases and 4 with connective tissue or immunoproliferative disorders. Six patients received 0.26-0.35 mg/kg body weight (B.W.)/day and 3 0.48-1.2 mg/kg B.W. on alternate days, for 10-16 months. Except for a child with chronic juvenile arthritis, who was also unresponsive to Prednisone, the therapeutic effects of Deflazacort were excellent. Steroid side effects present in 8 patients decreased or disappeared. Plasma Ca, P, Mg, creatinine, alkaline phosphatase, iPTH(1-34), urinary excretion of Ca, cAMP, and TRP remained normal. Plasma iPTH(1-84) remained normal in 5 children; in the other 4 patients it increased from normal to slightly elevated values. On Deflazacort, plasma calcidiol concentrations were within the normal range in 6/8 patients prescribed daily doses of vitamin D2 (1,600-2,400 IU) or calcidiol (20 micrograms). Plasma 1,25(OH)2D levels monitored in 5 children were also normal. The osteoporosis, evaluated on the tibial cortico-diaphyseal ratio and the trabecular aspect of bone radiograms, present in 5 patients, persisted in 1 and improved in the others. On Deflazacort, statural growth proceeded normally in all subjects, with a modest acceleration of growth velocity in 3 children. These results seem encouraging for extending clinical trials with Deflazacort to the active phase of pediatric diseases requiring glucocorticoid.

Elevated plasma 1,25-dihydroxyvitamin D concentrations in infants with hypercalcemia and an elfin facies.

We measured plasma concentrations of 1,25-dihydroxyvitamin D (1,25-(OH)2D) in the course of a 6-to-37-month survey of four children with hypercalcemia and an elfin facies (Williams syndrome). Levels of 1,25-(OH)2D were elevated (160 to 470 pg per milliliter) during the hypercalcemic phase of the disease, when the children were five to nine months old, and they decreased thereafter. Plasma 1,25 (OH)2D levels were higher than those found in three children (16 to 60 months old) with the elfin facies syndrome and no hypercalcemia (42 to 71 pg per milliliter) and eight children (1 to 36 months old) with hypercalcemia and no dysmorphy (12 to 140 pg per milliliter), including two children with vitamin D intoxication. Hypercalcemia in the three children with elfin facies was controlled by a low-calcium diet. Serum calcium levels fell to the normal range, and plasma 1,25-(OH)2D levels were normal for age (18 to 105 pg per milliliter) at 14 to 47 months of age, even after appropriate therapy had been discontinued. These observations suggest that hypercalcemia may be the consequence of abnormal synthesis or degradation of 1,25-(OH)2D in children with the elfin facies syndrome.

[Chondrodysplasia punctata congenita: a genetic heterogenous disease]. / Chondrodysplasia punctata congenita: een genetisch heterogeen ziektebeeld.

Chondrodysplasia punctata congenita is an entity of genetic heterogeneity characterized by the presence of stippled epiphyseal and extra-epiphyseal calcifications in roentgenograms. There are at least three distinct types which differ in their mode of inheritance: the autosomal recessive, the X-linked dominant and the autosomal dominant type. Recently a mesomelic type has been recognized. Its mode of inheritance is not known. A case of chondrodysplasia punctata congenita is presented with its signs and symptoms. The pregnancy was complicated by a sepsis. The mother used several drugs. The classification of the child which died after two days is difficult; she probably belongs to the mesomelic type. The diagnosis chondrodysplasia punctata congenita is mainly based on radiological examinations.

Rickets and alopecia with resistance to 1,25-dihydroxyvitamin D: two different clinical courses with two different cellular defects.

UNLABELLED: Two unrelated patients, aged 22 months and 31 months, with alopecia and rickets resistant to 1,25-dihydroxyvitamin D (1,25-(OH)2D] (vitamin D-dependency type II) presented with similar biochemical and radiologic features. They were treated with large doses of vitamin D3 derivatives [25-hydroxyvitamin D3 (25-(OH)D3), 1,25-(OH)2D3, and 1 alpha-hydroxyvitamin D3] for 28 months and 6 yr, respectively. In both patients, serum 1,25-(OH)2D levels remained high (approximately 10- to 100-fold normal) during the different therapeutic regimens. Circulating 1,25-(OH)2D and 24,25-dihydroxyvitamin D levels at various stages of the disease suggested in these children disturbances in the regulation of 25-hydroxyvitamin D (25(OH)D) 1 alpha- and 24-hydroxylase systems. In one child, all therapeutic trials were unsuccessful. Studies of her cultured skin fibroblasts showed low capacity (10% normal) for saturable (presumably receptor mediated) nuclear uptake of tritiated 1,25-(OH)2D3; the uptake process of nucleus associated 1,25-(OH)2D3 was normal in apparent affinity for 1,25-(OH)2D3 and in sedimentation velocity of nucleus-associated hormone. In the second child, correction of biochemical abnormalities, healing of rickets, and catch-up growth were obtained during similar therapeutic trials up to the age of 6 yr when a relapse occurred. This relapse has persisted for 2 yr in spite of similar or higher circulating concentrations of 25-(OH)D and 1,25-(OH)2D than those obtained previously when she was responsive to therapy. In her cultured skin fibroblasts, saturable high affinity nuclear uptake of 1,25(OH)2D was unmeasurable. IN CONCLUSION: 1) distinct patterns of clinical response can occur in patients with the syndrome of vitamin D-dependency type II, and can be associated with differing abnormalities in interaction of 1,25-(OH)2D3 with cultured skin fibroblasts; 2) aggravation of the resistance to 1,25-(OH)2D3 may occur during long term therapy in some patients.

Circulating vitamin D metabolite concentrations in children with nutritional rickets.

Serum calcidiol, calcitriol, and 24,25-dihydroxyvitamin D concentrations were measured in 20 children with vitamin D-deficiency rickets. Vitamin D metabolite concentrations were measured in 17 of 20 patients before treatment and in 14 of 20 patients after vitamin D administration. Conclusions are as follows. (1) Before treatment, serum calcidiol seems to be the best criterion of D deficiency, as it was low (less than 8 ng/ml) in 15 of 17 studied children, whereas calcitriol and 24,25-dihydroxyvitamin D concentrations ranged from undetectable to high values (350 pg/ml and 5.9 ng/ml, respectively). (2) Low calcidiol concentrations may occur despite recent vitamin D intake: low serum values were found in children given vitamin D2 up to two months after the onset of therapy (50 micrograms/day). (3) Elevated calcitriol serum concentrations were observed in all children after initiation of vitamin D therapy; these high concentrations persisted for four weeks or more, even after normalization of serum calcium, phosphorus, and parathyroid hormone values. (4) Healing of biochemical abnormalities can occur even in children with low circulating concentrations of calcidiol and 24,25-dihydroxyvitamin D.

[Measurements of plasma concentrations of active vitamin D metabolites in children: interest and limit (author's transl)]. / Mesure des taux circulants des métabolites actifs de la vitamine D chez l'enfant. Intérêt et limites.

This study of the three main vitamin D metabolites namely 25-(OH) D, 24, 25-(OH) 2D and 1, 25-(OH) 2D includes (1) a summary of the usual assay techniques, (2) a discussion about the concentrations and the role of these metabolites during the neonatal and childhood periods, (3) a report of the results obtained during the past seven years in our laboratory with comments on the interest and limits of these assays for the diagnosis of different types of rickets.