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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.

The regulatory functions of vitamins are described with particular reference to their importance in the metabolic processes of ageing. Although clear hypovitaminosis is uncommon, slight vitamin deficiencies are often encountered in the clinical practice. They cause a speed up of the organism deterioration. The nutritional requirement and the effect of vitamin A, B1, B6, B12, are rapidly reviewed. More attention is paid to the data about vitamin C, D and E. Vitamin C deficiency in elderly, especially in the hospitalized ones; whereas a high content of ascorbic acid in necessary in order to extend the life length and to achieve a good self-sufficiency. Also the deficiency of vitamin D and of its metabolites is frequent in the aged due to both a lower uptake and a scarce exposure to the sunlight. Low levels of vitamin D cause a worsening of bone tissue and consequent demineralization (osteomalacia and osteoporosis). Some aspects of ageing can be prevented by the supply of vitamin E, particularly the impaired bone trophism. The anti-oxidant power of tocopherol could also interfere some pathogenetic processes of ageing.

One of the most important complication of patients with chronic renal failure is osteodystrophy. This causes skeletal deformities, growth failure, bone pain and decreased physical activity. Osteodystrophy is more frequent among children than uraemic adults. In fact, 50-80% of children with chronic renal failure may occur in metabolic bone disease and the incidence tends to be higher in those children who have been in uraemic state for a long time before starting chronic haemodialysis. Osteodystrophy is a result of: 1) lesions of rickets; 2) lesions of osteitis fibrosa: 3) osteosclerosis. In contrast to adult, metastatic calcifications are virtually never observed in uraemic children. Hyperphosphoraemia, that is secondary to the reduction of G.F.R., may be the principal responsible of hyperparathyroidism that is the main cause of osteodystrophy. Hyperparathyroidism is also maintained and increased by deficit of 1,25(OH)2D3 which is responsible for lesions of rickets. Haemodialysis may markedly improve osteitis fibrosa and it is efficacious in reversing the mineral defect. Dialysate calcium concentration should be maintained at approximately 3,5 mEq/l. In this case we can raise serum calcium. On the contrary dialysate has to be lacking in phosphorus to correct hyperphosphoraemia. It must be noted that we have to prepare a dialysate with deionized water lacking in aluminum to avoid encephalopathy compliance.

Circannual rhythm of serum 25OH-cholecalciferol has been evaluated in 11 normal adult subjects. Blood samples were collected monthly. The pattern of serum levels of the metabolite was biphasic with the lower average values between January and June and maximal mean levels between July and October. Mean values were higher than in North-European countries. The estimated dietary intake of cholecalciferol was in the normal range. Therefore diet does not seem to account for the relatively elevated serum levels of the metabolite. On the contrary sunlight exposure appeared to have marked influence both on mean 250HD levels and on the seasonal rhythm. In spite of seasonal wide variation of serum 250HD levels, blood calcium and phosphate values were stable. The results of serum PTH assay favour the hypothesis that the maintenance of steady blood calcium levels may be due to seasonal variation of parathyroid secretion.