Vitamin D was discovered over 100 years ago and for a long time was mainly associated with its effects on the body's calcium-phosphate balance, i.e., rickets in children and osteomalacia and osteoporosis in adults. The discovery of the vitamin D receptor (VDR) in the 1970s in most human extraskeletal cells initiated several studies on the effects of vitamin D on numerous tissues.

The primary sources of vitamin D for humans are skin synthesis and intestinal absorption. However, these sources are relatively limited. Geographical location of Poland practically excludes the possibility of effective vitamin D synthesis in the months from October to April. Moreover, even a healthy and varied diet is not able to fully satisfy the body's demand for vitamin D. This raises the need for supplementation, both in the general population and in groups at risk of deficiency, from the first days of life to old age.

Depending on the source of origin, vitamin D occurs in two forms: vitamin D₂ (ergocalciferol - produced by plants, algae, and fungi) and vitamin D₃ (cholecalciferol - produced by animals). The total concentration of vitamin D in the human body is a result of natural synthesis processes occurring in the skin under the influence of sunlight, dietary intake, as well as supplementation.

Vitamin D supply is measured by the concentration of the sum of the metabolites 25(OH)D₂ and 25(OH)D₃. However, the assessment of bioavailability (efficiency of catabolic metabolism) is based on the ratio of 25(OH)D₃ to its catabolite metabolite 24,25(OH)₂ D₃. Zaopatrzenie organizmu w witaminę D mierzone jest stężeniem sumy metabolitów 25(OH)D₂ i 25(OH)D₃. Natomiast ocena przyswajalności (efektywności metabolizmu) wydawana jest na podstawie stosunku 25(OH)D₃ do jego metabolitu 24,25(OH)₂D₃.

Vitamin D is involved in a range of processes in the human body. It is responsible for regulating the calcium metabolism and adequate bone mineralisation. It regulates and influences cell proliferation and differentiation processes in the immune system, the activity of the renin-angiotensin-aldosterone system, and insulin secretion. Vitamin D has anti-inflammatory and antioxidant effects. It also modulates the normal function of the immune, nervous, muscular, and cardiovascular systems.

Vitamin D deficiencies can be associated with the development of numerous conditions such as osteoporosis, dental caries, depression, or atherosclerosis. Muscle aches, decreased ability to concentrate or increased incidence of seasonal infections may also occur. Vitamin D deficiency can increase the risk of complications during pregnancy and has a direct impact on the vitamin D supply to the foetus.

Overdose, although extremely rare, is a real risk in people taking very high doses of vitamin D. It leads primarily to hypercalcaemia (excessive calcium concentrations in the body) and may manifest with symptoms such as nausea, vomiting, abdominal pain, dehydration, decreased appetite, increased thirst and urination (polydipsia and polyuria), weight loss, and renal dysfunction.

According to the Polish recommendations for vitamin D supplementation and treatment (revised 2018), there are no indications for vitamin D determinations in the general population. In healthy individuals, only supplementation in regimens established for specific age groups is recommended, without the need for monitoring. On the other hand, an increasing number of clinical situations are being identified in which vitamin D concentration monitoring and its optimisation are important to mitigate the course or minimise complications arising from the underlying conditions. These conditions may include a range of disorders affecting the musculoskeletal system, digestion, absorption, and mineral metabolism, liver and kidney diseases, endocrine disorders, cardiovascular diseases, allergic, autoimmune, metabolic, and cancerous diseases.

Equally important are cases of hypersensitivity to vitamin D resulting from mutations within the genes encoding the vitamin D metabolising enzymes. This leads to a disproportionately strong response to supplementation and can result in overdose.

In conclusion, the question to be answered is: is it better to treat or prevent? Since maintaining an optimal level of vitamin D is so important, isn't it important to check how well the recommended treatment regimens are tailored to an individual's needs?

The vitamin D test at Masdiag Laboratory is based on the measurement of metabolite profiles: 25(OH)D₂ and 25(OH)D₃, and its result is expressed as the sum of 25(OH)D. In addition, the product of vitamin D metabolism - 24,25(OH)₂D₃ - is also measured, and the bioavalibility coefficient is calculated, indicating the current supply of vitamin D to the body based on the balance of absorption/production and excretion processes. Badanie witaminy D w Laboratorium Masdiag opiera się na oznaczeniu profilu metabolitów: 25(OH)D₂ i 25(OH)D₃, a jego wynik jest wyrażany jako suma 25(OH)D. Ponadto oznaczany jest produkt metabolizmu witaminy D – 24,25(OH)₂D₃, i wyliczany współczynnik przyswajalności, wskazujący na aktualne zaopatrzenie organizmu w witaminę D na podstawie równowagi procesów wchłaniania/wytwarzania i usuwania.

The test is performed using the isotopic dilution method and high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The use of LC-MS/MS technique provides analytical capabilities not achievable with other techniques. It allows high repeatability and accuracy of measurements. It ensures that the results obtained are not influenced by other substances, such as 3-epi-25(OH)D₃ or biotin.

An additional advantage is that the test can be performed with different materials: serum, plasma, or a dried blood spot.

Masdiag Laboratory participates in the international proficiency testing programme - Vitamin D External Quality Assessment Scheme (DEQAS)

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