Modern tendencies in diagnostics: prophylaxis and treatment of Vitamin D deficiency

Rudenko E.v. , Professor of Department of cardiology and internal diseases
Educational Institution Belarusian State Medical University

Early in XXI century, D-deficiency/insufficiency again took not only medical but medical-social importance. Based on statistics over 1 billion of people all over the world suffer Vitamin D deficiency (DVD) or its insufficiency. Studies of Vitamin D status in Europe via monitoring of 25(OH)D blood level demonstrated that only 13% of examined population reported its suboptimal content [1,2,3].
On the one side, such a wide prevalence of D hypovitaminosis is caused by objective demographic changes: evident population aging and natural growth of geriatric pathology due to either age disorders of functional regulation of organism or life conditions of elderly persons (unbalanced nutrition, low physical activities, insufficient sun exposure), on the other hand climatic changes related mainly to people activities (more cloudy days, less insolation inhibit Vitamin D production in organism). Shift of solar zenith angle subject to terrestrial latitude, season of the year or time of the day influences significantly Vitamin D3 (Cholecalciferol) synthesis. In areas of latitudes above or under 33o the production of Cholecalciferol is least intensive or absent during the most part of winter [4].
In the Republic of Belarus over 50% of women of all age groups evidence low Vitamin D in serum regardless of seasons; the rate of D hypovitaminosis is 79% in autumn-winter period and in spring-summer it is 75%. In men of middle age, the rate of Vitamin D hypovitaminosis is 73% in autumn-winter period and 57% in spring-summer [5, 6].
In recent years, genetic predisposition to DVD has been actively studied. The vitamin D receptor gene (RVD) is one of the central regulators in the endocrine system and acts as a candidate gene that determines the characteristics of human growth. It has been proven that mutations of this gene lead to rickets, osteomalacia, growth retardation, bone deformations and secondary hyperparathyroidism [1,4]. In addition, new data indicate the likely role of RVD polymorphism in the pathogenesis of bone damage and the development of secondary osteoporosis in rheumatoid arthritis and other autoimmune diseases [7,8].
Of particular interest in recent decades is the study of the role of vitamin D and its active metabolites in the functioning of the components of the immune system: lymphocytes, monocytes and dendritic cells. Studies have appeared that indicate the ability of 1,25-dihydroxy Vitamin D3 to induce macrophage fusion and differentiation processes, reduce the production of inflammatory mediators in autoimmune diseases, and regulate the cellular response to oxidative stress [7,9]. In total, more than 30 positive effects of Vitamin D on the immune system were found, which allows initiating further studies to investigate the possibilities of its use in the treatment of autoimmune diseases [10,11,12].

Figure 1. Stages of Vitamin D metabolism.

Figure 1. Vitamin D production, basic stages of its Metabolism and biological effect [13]

The term «Vitamin D» is defined as a group of chemicals used by each steroid, including the use of vitamins D2 (Ergopcalcipherol) and D3 (Cholecalciferol). Ergopcalcipherol is primarily found in plants derived from ergosterol, and cholecalciferol is a 7-dechydrocholesterol in the body and life under high soluble salt.

Synthesized in skin under UV rays, Cholecalciferol binds to specific vitamin D binding protein (DBP) (transcalcipherin) and is transferred to liver. Then in endoplasmic reticulum of hepatocyte its hydroxylation occurs at the 25th carbon atom with 25 (OH) D3 (Calcidol) formation, the latter binds to alpha-globulin and circulates in blood without altering calcium metabolism. The follow-up stage hydroxylation of 25 (UN) D3 under the influence of 1-alpha-hydroxylase enzyme occurs in mitochondrion of renal proximal channel cells. Consequently active metabolite of vitamin D -1.25 (OH) 2D3 (Calcitriol) and 24.25 (OH) 2D3 is synthesized. The first one has been termed lately as D-hormone because particularly this form of Vitamin D participates in calcium-phosphorus metabolism and also because of relation of specific nuclear receptors with Vitamin D (VDR) located in multiple tissues of human body manifests various biological effects, and the second one regulates parathyroid hormone (PTH) concentration by feedback [7,13].

So-called skeletal effects of Calcitriol are very important in metabolic processes in bone tissue. D-hormones increase Calcium absorption in intestine and its re-absorption in kidneys. Calcitriol enhances intestinal absorption of Calcium by stimulating the synthesis of Calcium-binding protein Calmodulin in enterocytes. Calmodulin in its turn transfers Calcium ions through intestinal wall and lymphatic vessels in vascular bed. Sufficient plasma Calcitriol level stimulates intestinal absorption of ionized Calcium by 2–3 times and of Phosphorus by 80%. Calcium reabsorption in renal tubules occurs in a similar way.
In bone tissue, Calcitriol stimulates the expression of receptor-activator of nuclear factor kB (RANKL) ligand, enhances osteoblast proliferation, synthesis of collagen and glycosaminoglycan. 1,25(OH)2D is a potent stimulator in vitro; in high doses 1,25(ОН)2D binds to VDR on osteoblasts and increases RANKL expression and release [11,14].
By interaction with VDR 1,25(OH)2D3 develops its genomic effect in various organs and cells presented in Table 1 1 [13].

Table 1 — Principle organs and cells with VDR

Vitamin D deficiency diagnostics
Currently, the clinical department of laboratory diagnostics is equipped with available standardized methods for determining its status in organism. DVD is detected using reagent kits to determine the level of total 25 (OH) D (includes 25 (OH) D2 and 25 (OH) D3) in blood serum using modern methods of mass spectrometry, competitive protein binding, high performance liquid chromatography, and radio-immune, enzyme immunoassay or immuno-chemiluminescent analysis. In a laboratory study, it is necessary to verify the reliability of the method used in clinical practice for determining 25 (OH) D against international standards (DEQAS, NIST), using the same method in the same laboratory. To assess the status of Calcidol with the use of Cholecalciferol or its active metabolites, it is recommended to take blood samples at least 3 days after the last dose. Determining the concentration of total 25-hydroxyvitamin D (25 (OH) D circulating in the blood is by far the best method for assessing and monitoring the status of vitamin D in clinical practice, since Calcidol has a long half-life of about 15–16 days [13].
The serum concentration of total 25-hydroxyvitamin D, depending on the measurement method, is expressed in nanograms per milliliter (ng / ml) or in nanomoles per liter (nmol / l). To compare the results, it should be borne in mind that 1 ng / m equals 2.5 nmol / L. Indicators of 25 (OH) D levels are variable and largely depend on diagnostic methods, the country’s geographical location, technical errors, and human factors.
To clarify the bone pathology caused by vitamin D deficiency, it is necessary to assess the levels of PTH, calcium, phosphorus, ALP, magnesium, β-cross-laps, osteocalcin in the blood serum, calcium / creatinine ratio in morning urine. At a level of 25 (OH) D less than 10 ng / ml, an in-depth examination of the patient is necessary to exclude osteomalacia (biopsy of the iliac wing), hereditary connective tissue diseases (genetic testing), determination of 1.25 (OH) 2D levels in the presence of chronic kidney diseases. In order to eliminate intestinal malabsorption, it is important to identify markers of celiac disease and other chronic inflammatory diseases of the gastrointestinal tract [4,13, 14].
Reference data of 25(OH)D level n and their interpretation are presented in Table 2. This concept of clinical interpretation of Calcidol level was developed by a large group of scientists within 200/2013 under the direction of Prof. P.Pludovsky and published in Practical recommendations on Vitamin D supply and treatment of its deficiency in the countries of Central Europe [15].

Table 2 — Reference parameters of 25(ОН)D in blood serum and their clinical interpretation

Indications to determine 25(ОН) D in blood serum:
1. Elderly persons staying long indoors;
2. Differential diagnostics of skeleton metabolic diseases (rachitis, osteomalacia, osteoporosis, etc.);
3. Detection of autoimmune and oncological diseases;
4. Apparent deficiency or extra body weigh/obesity;
5. Celiaс disease, malabsorption;
6. Before administration of osteoporosis therapy;
7. Menopause in women, hypogonadism in men;
8. Evaluation of dynamics in long intake of high doses of Vitamin D;
9. Emigrants from southern territories.
In 2013, the Ministry of Health of the Republic of Belarus approved the instructions for use «Methods for the diagnosis, prevention and differentiated treatment of vitamin D deficiency» (registration number 033–031313 from 06/14/2013) [16]. An appendix to this instruction is an algorithm for the diagnosis and prevention of DVD, which can be used to identify risk groups, determine indications for a study of the plasma level of 25 (OH) D and to determine the required dose of Cholecalciferol (Fig. 2).

Algorithm of diagnostics and prophylaxis of Vitamin D deficiency in the Republic of Belarus Vitamin deficiency group of risk

Correction methods of Vitamin D deficiency:
1. Healthy foods;
2. Food fortification with Cholecalciferol;
3. Sufficient natural sun exposure (main source);
4. UV tubes;
5. Ergocalciferol (D2) intake;
6. Cholecalciferol (D3) drugs’ intake;
7. Active metabolites of Vitamin D;
8. Parenteral introduction of Vitamin D-drugs;
Recommendations for diet
These foods have relatively high levels of vitamin D: fatty varieties of marine fish. scomber, salmon, tuna, mackarel and herring are sources of vitamins D. The liver of cod and halibut, caviar, seafood, oil sprats, beef and pork liver, cheese, egg yolks, cheese, and butter are also rich in vitamin D. The highest content of Vitamin D in fish oil, 100 grams of which contains 250 micrograms of vitamin. Prepackaged gelatin capsules contain IU500 of vitamin A and IU50 of vitamin D. It is worth noting that the composition of fish oil also includes Vitamin A (30,000 g per 100 grams), which overdose is characterized by headache, weakness, dry skin, joint pain, cracked lips, rare hard hair, dry rough skin. It should be remembered that high doses of vitamin A are teratogenic. Potato, parsley, nuts, seeds, mushrooms, oatmeal, and products such as urtica, horsetail, dandelion greens, and lucerne should be noted among plant foods containing vitamin D.
Publications provide tables on the content of vitamin D in foods. However, in general, in the daily diet with the nutrition traditional for Belarusians, its content is no more than IU100-200. In many countries, fortification of some of the products most used by the population is carried out: flour, bread, milk, juice, yogurt, vegetable oils, and others. In the UK, studies have been conducted on the economic assessment of the enrichment of wheat flour with vitamin D. As a result, a forcible economic argument for enrichment of wheat flour with vitamin D (£ 9.5 per QALY) was proved.
Scientists estimate that only wheat flour enrichment reduced D hypovitaminosis in the population of country D by 25% [17].
The main source of vitamin D for most people is its formation when exposed to sunlight on the skin, usually within 1000–1500 hours in spring, summer and autumn. Vitamin D formed in the skin can remain in blood at least twice as long as supplied with food. When an adult in a bathing suit is exposed to one minimal erythema dose of ultraviolet radiation (a slight pinking of the skin 24 hours after exposure), the amount of vitamin D produced is equivalent to ingestion of IU10000-25000.
The synthesis of Cholecalciferol in human skin can be influenced by many factors, the most significant of which are the use of sun protective aids, skin pigmentation, the presence of scars after burns, psoriasis, decrease in the content of 7-dehydrocholesterol in the skin in the elderly people, time of year, geographical location, duration of light days and others [2,4,17].

Pharmacological correction of D hypovitaminosis
Cholecalciferol and its active metabolites are available in market as solutions, capsules, pellets IU200 to IU50000. In clinical practice doctors of various specialization DVD monotherapy subject to 25(OH)D level adopts either high individual doses or lower doses for prophylaxis and treatment (IU500-2000) without lab monitoring of Vitamin D also in combination with Calcium-drugs.
Table 3, compiled on the basis of generalization of the data obtained during the study of international recommendations for the diagnosis and correction of D hypovitaminosis, gives indications for administration of vitamin D3 in various doses, depending on initial 25 (OH) D and the incidence of laboratory tests to monitor its status in order to clarification of the need for correction of ongoing therapy and the exclusion of a possible overdose of Cholecalciferol [14,18,19].

Table 3. Indications for usage of prophylactic and therapeutic doses of Vitamin D3

According to practical recommendations proposed by the US Institute of Medicine in 2011, a differentiated approach to prescribing daily doses of Cholecalciferol from IU400 IU10000 can be recommended for the prevention of DVD [18]. Some aspects of these recommendations are presented below:
1. For healthy population aged 18–50 years, with the aim of preventing DVD, it is recommended to receive at least IU600-800 of vitamin D per day to achieve suboptimal levels of 25 (OH) D of more than 20 ng / ml. To maintain a concentration of 25 (OH) D of more than 30 ng / ml, IU1500–2000 of Cholecalciferol per day is needed;
2. Persons over 50 years of age for the prevention of DVD need at least IU800-1000 of vitamin D per day;
3. In recent meta-analyzes based on double-blind randomized clinical studies, it was shown that in the population of elderly men and women, an additional intake of vitamin D at a dose of IU800-1000 reduced any non-vertebral fractures, hip fractures, and falls by approximately by 20%;
4. Scientific studies in people over 65 to evaluate the effect of IU800 of vitamin D per day on muscle strength, impaired coordination of movements and the frequency of falls revealed the following results: muscle strength increased by 4–7%, coordination of movements improved by 28%, and incidence of falls decreased by 35–72% based on reports from various sources.
5. Pregnant and feeding women for DVD prophylaxis need at least IU800-1200 of Vitamin D daily. If factor of risk of DVD are present, control initial 25(OH)D and subject to the results select an individual dose OI15000-4000 daily with further monitoring of 25(OH)D dynamics every 3 to 6 months.
5. For people with overweight or malabsorption Vitamin D3 daily dose can be increased to IU4000 and over.
Table 4 summarizes various doses of Cholecalciferol drugs registered by Minskintercaps U.v. in MH Belarus providing individual pattern of DVD treatment subject to a special clinical case [20].

Table 4 — Cholecalciferol drugs registered in MH Belarus by pharmaceutical enterprise Minskintercaps U.V.

Note. 1 mg=IU40
Signs of Vitamin В overdose and intoxication are rare and associated mainly with high doses for a long period. Clinical symptoms in this case are anorexia, nausea, polyuria, constipation, asthenia, weight loss, headache, depression, thirst, muscular rigidity, soft tissue calcification, nephrocalcinosis, and hypertension.
Laboratory signs confirming an overdose of vitamin D are hypercalcemia, hypercalciuria (urine Ca ratio (mmol / L) / urine creatinine (mmol / L) more than 0.57), an increase in 25 (OH) D level above 100 ng / ml. Hypercalcemic crisis, developing with an increase in blood calcium levels to 4 mmol / l, can lead to death as a result of inhibition of nervous activity and coma.
Contraindications of vitamin D3 drugs in adults are: hypercalcemia, hypercalciuria, nephrocalcinosis, nephrolithiasis, hypervitaminosis, a tendency to allergic reactions to components of the composition of the drug. Vitamin D preparations are not prescribed for granulematosis, sarcoidosis, bone metastases, Williams syndrome due to the increased risk of hypercalcemia and hypercalciuria [13,14,20].
Conclusion. When prescribing calcium and vitamin D preparations, the attending physician should make every effort to achieve an adequate adherence to treatment and to obtain the best result in relation to primary and secondary prevention of osteoporotic fractures. At the same time, regular laboratory monitoring of calcium-phosphorus metabolism is necessary to exclude hypercalcemia, especially when prescribing high doses of vitamin D. Monotherapy of DVD with Cholecalciferol is carried out for years, and in the absence of effect in some specific clinical situations, especially with renal osteodystrophy, its active metabolites Calcitriol or Alphacalcidolum.

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20. Instruction for usage of D3 caps is available on site http://from 00.00.2019: (will be inserted when ready)