Volume 8 · Number 2 · June 2016
- Secondary hyperparathyroidism due to vitamin D deficiency [55-60]
- Analysis of mechanical behavior variation in the proximal femur using X-FEM (Extended Finite Element Method [61-69]
- Comparison between two automated chemiluminescence immunoassays for quantifying 25 (OH) vitamin D [70-74]
- Study of the microstructure of femoral patients with hip osteoarthritis and hip fracture by microCT [75-81]
- Osteomalacia in a young adult [82-86]
Subclinical deficiency of vitamin D or vitamin D deficiency is prevalent throughout the world, and there is great variability depending on the geographic region, genetic factors and lifestyle considerations.
Moreover, researchers now believe that serum 25-hydroxyvitamin D (25OHD) levels are the best indicator of vitamin D, although there are methodological issues that limit comparability between studies and how to establish deficiency cutoffs.
There are several criteria to establish the optimal level of 25OHD, which include the degree of maximal suppression of PTH, the intestinal absorption of mediated calcium 1,25(OH)2 vitamin D or reduction of fractures. Regarding the former, several studies have analyzed 25OHD concentration required for maximum suppression of PTH and offer variable results. This has led some researchers and scientific entities to recommend 25OHD levels above 20 ng/ml (Institute of Medicine, IOM) while others advise over 30 ng/ml (Endocrine Society, International Osteoporosis Foundation). The application variable for these recommendations has generated considerable confusion in clinical practice.
Introduction: Vitamin D is increasingly recognized as playing a significant role in combatting many diseases. One is the development of secondary hyperthyroidism due vitamin D deficiency. To date, laboratory quantification methods of serum vitamin D were not well standardized. It could not be established with certainty from which levels of vitamin D certains abnormalities take place, like an elevation of PTH. The present study was aimed at determining below what vitamin D levels we will find abnormally high levels of PTH, carrying out the vitamin D determination in the laboratory with a standardized, reliable technique.
Methods: This descriptive, retrospective study was conducted with patients over 18 years in which determinations were made simultaneously with PTH, 25 (OH) vitamin D (25OHD) and which also have normal values ??of calcium, glomerular filtration rate and phosphorus.
For determining vitamin D, standardized electrochemiluminescence method was used with gas chromatography-mass spectrometry method. Using the Stava version 11 statistical program, the 25OHD was calculated where PTH value was above 70 pg/ml with greater sensitivity and specificity.
Results: In all, 4,083 patients were included, of whom 2,858 were women (70%) and 1,225 (30%) males. The mean age of the study population was 60.60 years (standard deviation, 15.29). 74% of the population had a serum PTH under 70 pg/ml (normal values) and 26% had a serum PTH higher tan 70 ng/ml. By constructing the ROC curve levels of 25OHD, depending on PTH values ??below or above 70 pg/ml, the area under the curve was 0.5962 (p<0.0001). The cut having jointly account the sensitivity and specificity that determined vitamin D levels to predict PTH values ??above 70 pg/ml was 24 ng/ml. Of the patients with normal PTH, 71% presented normal vitamin D values, while patients with elevated PTH (Greater than 70 pg/ml), almost half had a vitamin D below 24 ng / ml, which increased as the PTH percentage was elevated. Conclusions: The 25OHD value that presents better specificity and sensitivity to predict abnormally high PTH is 24 ng/ml, which is higher than the level reported in previous work, (about 18 ng/ml) value. The results of this study, carried out with an appropriately calibrated method, showed that 44.9% of patients with vitamin D values of less than 24 ng/ml PTH had abnormally high levels, with a normal value ??of calcium and phosphorus and normal renal function. This percentage is less in those individuals between 18 and 40 years (24%) and reaches 49% beyond 60 years. These patients could be treated with vitamin D to prevent possible secondary hyperparathyroidism due to vitamin deficiency. It is noteworthy that the method of determining vitamin D used must be properly standardized with respect to gas chromatography-tandem mass spectrometry method.
Analysis of mechanical behavior variation in the proximal femur using X-FEM (Extended Finite Element Method)
Introduction: For years, the human femur has been extensively studied experimentally with in vitro analysis. Nowadays, with computer advances, it can also be analyzed numerically. Some authors report the usefulness of finite method in predicting the mechanical behavior of this bone. There are many possibilities using the synergy between the method finite element and experimental trials. In this paper, for example, we study how they affect different osteoporotic simulations involving femur fracture loads.
The aim of this study is to predict hip fracture, both the load to which this occurs as the propagation of the crack in the bone. By applying the finite element method to the field of bio-mechanics, simulation can be carried out to show the behavior under different bone load conditions.
Material and methods: Using DICOM images, CT scan of the proximal end of the right femur of a male has been obtained bone geometry. By a computer program they have been generated dependent mechanical properties of the BMD each voxel, and then used a finite code to apply different load configurations and study values ??bone fracture elements. The numerical model has been validated in the literature.
Results: Load breaking in lateral fall configuration is approximately half the load in the case of the normal position, which agrees with different experimental studies published.
In addition, we have studied various load conditions in everyday situations, where it was observed that the load fracture is minimal in mono-podal position. Osteoporotic conditions have also been simulated which confirmed that the load fracture has been reduced by decreasing mechanical properties.
Conclusions: By using the finite element method in conjunction with DICOM medical imaging, it is possible to study the biomechanics of the hip and obtain an estimate of bone failure. In addition, different load configurations can be applied and vary the mechanical properties of bone to simulate the mechanical behavior of low osteoporotic conditions.
Introduction: Quantifying total blood 25 (OH) vitamin D is the most accurate marker of an individual´s vitamin D status. The gold standard technique for measurement is liquid chromatography tandem mass spectrometry (LC-MS/MS), although currently clinical laboratories tend to use chemiluminescence techniques. The objective of this study was to compare 25 (OH) vitamin D concentrations obtained by two commercially-produced automated methods and study the correlation of these methods with the LC-MS/MS reference technique.
Material and methods: The 25(OH) vitamin D levels were quantified in 1,000 serum samples from the Jimenez Diaz Biochemistry Foundation Laboratory using 2 automated methods for chemiluminescence detection: ADVIA CENTAURO® (SIEMENS) and LUMIPULSE® G1200 (Fujirebio). Among all the samples tested, the 50 most discordant to each other were sent to be evaluated by LC-MS/MS reference technique.
Results: The results indicate that there is good correlation between the two methods: CCI=0.923 (0.914-0.932), with the G1200 LUMIPULSE® ; values 10% being higher than CENTAURO®. Regarding the 50 samples selected, we can see that there is a good correlation between the two immunoassays with LC-MS/MS, although both methods significantly underestimate 25 (OH) vitamin D results with respect to the gold standard.
Discussion: Although both techniques are suitable for use, it is worth considering whether the worldwide vitamin D deficiency epidemic is due to the analysis methodology used. This variability between immunoassays could be solved by standardizing the different commercial techniques in line with NIST-produced reference materials.
Whereas bone mineral density (BMD) is characteristically low in osteoporosis, it has been postulated that in osteoarthritis BMD is increased. We aimed to check this concept by analyzing bone volumen and structure in the femoral heads of patients with hip fractures (n=10) and with hip osteoarthritis (n=9). Unexpectedly, the analysis of microstructural parameters by microCT did not reveal significant differences between both groups. In addition, we did not find a significant decline in the trabecular bone volume across the age range studied. These results suggest that the evolution of the trabecular bone of the femoral head is different from the age-related decrease of bone mass in other regions of the skeleton. Elucidating the mechanism involved could suggest new approaches to treat the bone loss associated with aging.read more
Cases of hypophosphatemic osteomalacia respond to various causes, both genetic and acquired. Some variants of mesenchymal tumors produce inappropriate amounts of fibroblast growth factor 23 (FGF-23), a mediator which induces renal phosphate loss. The biochemical picture is characterized by hypophosphatemia, decreased tubular reabsorption of phosphates, low or inappropriately normal serum calcitriol and high or unusually normal levels of FGF-23 plasma. This paraneoplastic syndrome is called tumor-induced or oncogenic osteomalacia.
There are a limited series of published cases, although it has been increasingly accepted in recent years. Diagnosis may be complex given its low incidence, the difficulties in localizing the tumors and heterogeneity in histopathologic interpretation. Complete surgical removal has healed, but there may be recurrences whereas phosphorus and calcitriol oral supplements offer alternative medical treatment.
In recent years there has been an enormous increase in the number of scientific publications 1,2, to such an extent that it is now impossible for us to read even 1% of what is coming out in our area of expertise or into the fields which interest us. The proliferation of scientific periodicals in general and medical journals in particular may be attributed to many factors. Among these we would highlight the Internet and changes in the very raison d’etre of such publications. Here we will comment on some aspects that have led to this situation.