Mìžnarodnij Endokrinologìčnij Žurnal (Sep 2021)
Vitamin D dosage
Abstract
Despite its historical name, vitamin D is not a vitamin at all but a hormone that, when activated, is a metabolically active steroid fat-soluble hormone that acts on cellular receptors. Vitamin D hormone is synthesized endogenously and then metabolized in the body, provi- ding that there are the necessary precursors and some factors — the effects of ultraviolet light on the skin. At the same time, vitamins themselves are nutrients, co-factors of biochemical reactions that are not synthesized in the body and cannot interact with receptors, consumed with food, so the hormone D is not a vitamin. Disputes about its use and dosage continue throughout the study period of vitamin D hormone. Most reputable experts in Europe and the USA support the need to replenish and maintain a normal level of vitamin D, believing it to be completely safe and useful. In 2011, the US Endocrine Society issued clinical practice guidelines for vitamin D, indicating that the desired serum concentration of 25(OH)D is > 75 nmol/l (> 30 ng/ml) to achieve the maximum effect of this vitamin on calcium metabolism, bone, and muscle metabolism. According to them, for a consistent increase in serum 25(OH)D above 75 nmol/l (30 ng/ml), adults may require at least 1,500-2,000 IU/day of additional vitamin D, at least 1,000 IU/day in children and adolescents. The most common form of thyroid dysfunction is secondary hyperparathyroidism, which develops due to vitamin D defect/deficiency (80–90 %). Non-optimal serum concentrations of 25(OH)D lead to secondary hyperparathyroidism, potentially leading to decreased bone mineralization and, ultimately, to an increased risk of osteopenia, osteoporosis and fractures, cardiac arrhythmia, and increased blood pressure. Vitamin D is most commonly used at a star- ting dose of 5,000 IU daily for 2–3 months, then transferring patients to maintenance doses of 2,000–4,000 IU/day daily that are consi-dered safe. However, it should be noted that some patients will need constant administration of 5,000 IU of vitamin D per day for a long time (years) to maintain the target optimal level of 25(OH)D in the blood, especially in patients with normocalcemic forms of secondary hyperparathyroidism.
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