[Assay of serum 24,25-dihydroxycholecalciferol by a competitive protein binding method]

24-25(OH)2 D3 is a vitamin D metabolite due to renal 24-hydroxylation of 25OHD3. The metabolite has some important biological functions on the bone and intestine. Its affinity to the D serum binding protein allows a competitive binding protein assay to be carried out as for 25OHD3, following a chromatographic purification step on Sephadex LH 20. Serum levels of the metabolite in 18 control subjects were found to be 2,69 +/- 1,34 ng/ml while 25OHD3 was 17,41 +/- 7,39 ng/ml and the ratio 24-25(OH)2D3 /25OHD3 in the serum was 0,15. The assay of 24-25(OH)2D3 is useful for physiological studies and for identification of vitamin D depletion states.

[Bone histomorphometry: methodological criteria in the study of metabolic skeletal diseases]

The present study deals with the appropriate statistical approach to the histomorphometric technique carried out on bone tissue with the Merz and Schenk integrating eyepiece. Statistical analysis of the results obtained from ten bone biopsies of renal osteodystrophic patients enabled to calculate the values of standard errors for each histomorphometric parameter as a function of measured histological fields. The examination of 42 fields chosen at random on histological sections from different sites of the bone biopsy guarantees sufficiently low standard error values. This technique is of invaluable help in the study of metabolic bone diseases, and extremely useful in the evaluation of treatment trials in renal osteodystrophy.

Albright's hereditary osteodystrophy

The authors observed different clinical forms of Albright's hereditary osteodystrophy in 4 members of a family (two sisters, their mother and the maternal grandfather). The sisters were affected by pseudohypoparathyroidism type I, the older manifested the hypocalcemic variety, the younger the normocalcemic variety; the mother and the grandfather presented only with short stature and subcutaneous calcifications. The variety of clinical and biochemical alterations observed in these 3 generations supports evidence that Albright's hereditary osteodystrophy has a broad spectrum and that distinctions between the various forms of pseudohypoparathyroidsim should not be rigidly considered.