Volume 13 · Nº 2 Suppl · Sep 2021
- Methods for determining vitamin D and its metabolites. Threshold value of bone manifestations [4-10]
- The role of new imaging techniques in predicting fracture risk [11-17]
- Genetic studies in the diagnosing of osteoporosis and other metabolic bone diseases [18-25]
- FGF-23 and pth, mirror hormones. Their role in bone metabolism[26-30]
- Health and economic impact of the use of vitamin D/calcium for fracture prevention: literature review [31-37]
Since the time of its discovery a century ago, there have been advances into what was erroneously called “vitamin” D. It is now acknowledged that it is not a vitamin, though we continue to use that term out of custom and tacit consensus. In fact, it is an endocrine system, the vitamin D endocrine system (VDES), similar to that of other steroid hormones. Cholecalciferol or “vitamin” D3, is the threshold (physiological) nutrient of the system, synthesized from 7-dehydrocholesterol, which is produced, and found, from single-celled organisms to the skin of higher animals, including human. This route represents around 90% of the physiological contribution to the body, the rest is obtained through diet. There is another isoform, of nutritional or pharmacological contribution, ergocalciferol, “vitamin” D2 or produced by ultraviolet irradiation of ergosterol contained in fungi, yeasts, etc….
In 1994, the WHO defined criteria for the diagnosis of osteoporosis using the measurement of bone mineral density (BMD). The DXA technique has established itself as the dominant technology for quantifying BMD due to:
a) strong correlation between BMD measured by DXA and bone strength in biomechanical studies,
b) Epidemiological studies that show a strong relationship between the risk of fracture and BMD,
c) For its use in clinical trials of treatments for the selection of subjects and monitoring based on its excellent precision and low radiation dose.
DXA is indicated to diagnose osteoporosis, assess fracture risk, and monitor changes in BMD over time. In recent years, there have been improvements to the initial DXA technology and it is used for other measurements beyond BMD (eg, femur geometry, vertebral fracture detection, body composition analysis).
The nucleus contains most of the genetic information, distributed throughout the approximately 3 billion nucleotides of human haploid DNA. The approximately 21,000 genes that encode the proteins necessary for the various organic functions are represented there, as well as an indeterminate number of genes that are transcribed into RNAs that do not encode proteins, but have regulatory functions.
Mitochondrial DNA is smaller, having about 16,000 nucleotides, with genes to encode 13 proteins and 24 non-coding RNAs (transfer and ribosomal).
DNA changes that lead to disease can be classified according to various criteria, including:
Conventionally, calcium, phosphorus, calcitriol and PTH were considered the only regulators of bone and mineral metabolism. In recent years, this axis of regulation has been complicated due to emergence of other factors with a crucial role in bone and mineral metabolism, such as fibroblast growth factor 23 (FGF-23) and the so-called klotho anti-aging protein.
Biological actions of FGF-23 and PTH
Biological action of FGF-23
FGF-23 is a 251 amino acid protein synthesized and secreted by bone cells, mainly osteoblast. FGF-23 has been identified as the main regulatory factor of phosphorus metabolism, a critical element for maintaining skeletal integrity and for the development of multiple enzymatic processes. In addition, in the last decade it has been attributed a notable role in the pathophysiology of vascular calcifications and cardiovascular disease (CV), both in the general population[4-6] and in patients with chronic kidney disease.
Health and economic impact of the use of vitamin D/calcium for fracture prevention: literature review
Osteoporotic fractures, especially those of the hip, are one of the main causes of disability in the elderly population, triggering a considerable decrease of life quality and lifespan. Besides, more than 30% of people die during the first year after suffering one of these fractures. In 2010, the European Union recorded nearly 3.5 million fragility-induced fractures that led to 43,000 deaths. From an economical point of view, these fractures meant an expenditure of 37 billion euros, a sum that is expected to rise by 52% in 2025.
Vitamin D and calcium are essential compounds for bone metabolism and prevention of osteoporotic fractures. Two recent meta-analyses have reported that low levels of 25(OH)D are related to the increase of fragility-induced fractures due to bone mass loss and bone structure deterioration[3,4].