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Biomedical subjects

P Lips

Publications and source records attributed to P Lips.

161 records · Page 9Linked to original sources
PubMed1985

Bone mineral content of transilial biopsies in patients with hip fracture.

In a survey of 125 patients with hip fracture vitamin D deficiency was frequently observed, but overt osteomalacia was not found in the bone biopsies (Lips et al., 1982). In order to detect a possible hypomineralization in these vitamin D-deficient patients, we measured the bone mineral content in 64 transilial biopsies, embedded in methylmethacrylate for histomorphometric evaluation. The results were compared with those of 18 bone samples obtained at autopsy from subjects who did not suffer from metabolic bone disease. The calcium:hydroxyproline ratio, the phosphorus:hydroxyproline ratio, and the calcium:phosphorus ratio were similar in the two groups. The magnesium:hydroxyproline ratio was higher in the hip fracture group than in the controls. The ratios did not correlate with serum concentrations of the vitamin D metabolites. The results are not consistent with a decreased bone mineralization in patients with hip fracture.

Aged↗
PubMed1985

[Vitamin D deficiency and hip fracture].

Vitamin D deficiency is common in the elderly, especially in patients with hip fracture. Elderly people infrequently stay outside in the sunshine, and nutrition is deficient in vitamin D. In addition, the hydroxylation of vitamin D into active metabolites decreases with age. Vitamin D deficiency ultimately leads to osteomalacia, but in an earlier stage it causes secondary hyperparathyroidism, which is accompanied by increased bone turnover and cortical bone loss. Along these pathways vitamin D deficiency may contribute to the pathogenesis of hip fractures. In a survey in Amsterdam vitamin D deficiency was observed in more than 60% of the patients with hip fracture. Transilial bone biopsy showed signs of high turnover and cortical bone loss in more than 20% of patients. The elderly which are institutionalized carry an increased risk. Prevention or vitamin D deficiency is possible by adequate exposure to ultraviolet light. Primarily, the elderly should be encouraged to go out into the sunshine regularly. Advice on nutrition may be given additionally. When sunshine exposure is negligible, as in many disabled and institutionalized elderly, a daily supplement of vitamin D3 400 IU should be given. Preventive measures have to be evaluated prospectively. Vitamin D deficiency is not the most important risk factors for hip fractures, but the easiest to correct.

Adult↗
PubMed1985

Vitamin D status in urinary calcium stone formation.

Serum vitamin D metabolites were measured in 160 normocalcemic urinary calcium stone formers and in 217 control subjects. No difference in concentrations of 25-hydroxy-vitamin D (25[OH]D), 24,25-dihydroxyvitamin D (24,25[OH]2D), and 1,25-dihydroxyvitamin D (1,25[OH]2D) was found between stone formers and control subjects. Values for 25(OH)D and 24,25(OH)2D were higher in hypercalciuric stone formers than in normocalciuric stone formers independent of seasonal fluctuation. No difference in concentration of serum 1,25(OH)2D was found between hypercalciuric and normocalciuric stone formers. No correlations were present between the serum concentrations of the measured vitamin D metabolites and of measures of calcium and phosphate metabolism. These findings suggest no major pathophysiologic role of the main vitamin D metabolites in urinary calcium stone formation.

24,25-Dihydroxyvitamin D 3↗
PubMed1984

Measurement of vitamin D metabolites in anephric subjects.

Circulating concentrations of 1,25-dihydroxyvitamin D, 24,25-dihydroxyvitamin D and 25-hydroxyvitamin D were measured in 21 anephric subjects. 13 subjects had no therapy with vitamin D, dihydrotachysterol or 1 alpha-hydroxyvitamin D3. In 7 subjects of this group 1,25-dihydroxyvitamin D was undetectable (less than 5 pmol/l). In the other 6 patients concentrations ranged from 10 to 43 pmol/l (reference value 111 +/- 33 pmol/l). All subjects taking high doses of vitamin D showed detectable 1,25-dihydroxyvitamin D concentrations in the same range. Dihydrotachysterol therapy caused spuriously high '1,25-dihydroxyvitamin D' values, probably by interference of a metabolite of dihydrotachysterol in our assay. In subjects on vitamin D or dihydrotachysterol therapy 25-hydroxyvitamin D concentrations were significantly elevated (314 +/- 146 nmol/l and 98 +/- 19 nmol/l, respectively; reference value 52 +/- 22 nmol/l). Concentrations of 24,25-dihydroxyvitamin D were only measured in subjects without vitamin D2 intake. In general very low but detectable concentrations were found. One subject on a high dose of vitamin D3 showed a 24,25-dihydroxyvitamin D3 concentration of 10.2 nmol/l (reference value 4.4 +/- 2.9 nmol/l). Our results therefore confirm earlier reports on extrarenal synthesis of 24,25-dihydroxyvitamin D and suggest that there may be extrarenal production of 1,25-dihydroxyvitamin D as well.

24,25-Dihydroxyvitamin D 3↗
PubMed1984

An international comparison of vitamin D metabolite measurements.

An international 19-laboratory survey was organized to compare assays for 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D in plasma. Each participant received two ethanolic standard solutions of each metabolite and eight plasma samples. Each laboratory used its usual procedures. Mean interlaboratory coefficients of variation (CVs) for the eight plasma samples were 35%, 43%, and 52% for 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D, respectively. Average CVs for the standard solutions were 27%, 23%, and 25%, respectively. Of the eight plasma samples, five had the same concentration for one of the metabolites. One sample was diluted to 0.6 times its original concentration and three samples were fortified with one or more of the metabolites under investigation. Fourteen of 18 laboratories (78%) could distinguish between the five unchanged samples and the modified ones with their 25-hydroxyvitamin D assay. Nine of 12 (75%) could distinguish the modified samples from the other samples with the 24,25-dihydroxyvitamin D assay. Only eight of 15 (53%) could do this their 1,25-dihydroxyvitamin D assay. Values from different laboratories evidently cannot be intercompared without making an actual comparison of the assay procedures. Furthermore, in case of clinical applications of these assays, each laboratory should establish its own reference values and should continually use an internal reference sample to assess the precision of the procedures.

24,25-Dihydroxyvitamin D 3↗
PubMed1984

Radiologic morphometry in patients with femoral neck fractures and elderly control subjects. Comparison with histomorphometric parameters.

Radiologic morphometry was performed in 125 patients with femoral neck fractures and 74 elderly control subjects to evaluate simple parameters for screening of the population at risk. Reproducibility of metacarpal cortical thickness was high when measured in six metacarpals. Values of this parameter were similar in patients and control subjects. Reproducibility of the Singh index was poor. The patients with femoral neck fractures had a higher vertebral index, more vertebral crush fractures, and a lower Singh index than the control subjects. There was no significant difference in these radiologic indices between cervical and intertrochanteric fractures. The radiologic indices correlated poorly with each other and with histomorphometric data from transilial bone biopsies of the patients. Stepwise discriminant analysis allowed correct classification as patient or control subject in only 69.8% of the cases, with the Singh index having the highest predictive value. The reported observations indicate a need for a more accurate technique for local assessment of the bone mass in the femoral neck.

Aged↗
PubMed1983

Hyperparathyroidism following irradiation of benign diseases of the head and neck.

In a series of 73 consecutive patients with hyperparathyroidism (HPT) eight patients gave a history of irradiation of head and neck because of benign diseases. The average interval between irradiation and definite diagnosis was 34 years. Intermittent hypercalcaemia was found in three patients. Microscopic examination of pathologic parathyroid glands of three patients showed a predominance of oxyphil cells. Thyroid abnormalities occurred more frequently in irradiated patients than in nonirradiated patients with HPT. Reviewing clinical and experimental data an etiologic role of irradiation in the pathogenesis of HPT appears present.

Adolescent↗
PubMed1981

Simultaneous determination of 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D in plasma or serum.

We describe a simultaneous assay for the principal vitamin D metabolites: 25-hydroxyvitamin D, 24-25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D. Special attention has been paid to simplification of the extensive extraction and purification procedures used in previously described simultaneous assays. All three metabolites were isolated with a single extraction step, followed by only one gradient liquid-chromatographic procedure. For final quantitation we used competitive protein binding assays, involving readily available binding proteins and commercially purchased tritiated vitamin D metabolites. Concentrations in the plasma of healthy subjects (mean age, 27 years), sampled during December were 51 (SD 17) nmol/L, 4.1 (SD 1.3) nmol/L, and 124 (SD 26) pmol/L for 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D and 1,25-dihydroxyvitamin D, respectively. Intra- and interassay CVs for the three metabolites were 4.4 and 3.9%, 6.7 and 8.0%, and 7.0 and 4.8%, respectively.

24,25-Dihydroxyvitamin D 3↗
PubMed1978

Mean wall thickness of trabecular bone packets in the human iliac crest: changes with age.

The mean wall thickness (MWT) of packets of trabecular bone was measured in undecalcified iliac crest bone samples of 36 normal subjects (14 female and 22 male) under polarized light. The mean wall thickness was 49.7 +/- 8.7 microns at a mean age of 50.9 years. There existed a significant decrease of MWT with advancing age. With an appositional rate of 0.72 micron/day, the mean formation time of iliac trabecular bone packets is 69 days. The decrease of MWT with age corresponds to a decrease in bone formation at the basic multicellular unit (BMU) level with aging and can partly explain the physiological senile osteopenia.

Adolescent↗