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Biomarkers of Vitamin D Sufficiency: Vitamin D metabolite levels do not depend on 25-Hydroxyvitamin D2 levels in healthy Turkish individuals

Year 2025, Volume: 17 Issue: 1, 84 - 90, 27.03.2025

Cüneyd Yavaş , Nezih Hekim , Lütfiye Karcıoğlu Batur , Recep Eröz , Ahmet Özaydın

Abstract

Objective: Patient-specific factors may influence the dose of supplemental vitamin D necessary for adequacy, and it is important to verify which metabolite is considered clinically meaningful in order to prescribe vitamin D supplements. We assessed the relationship between 25(OH)D2 and free vitamin D levels in healthy Turkish population and those with vitamin D deficiency.
Methods: Blood samples were taken from 92 healthy adults over the age of 18, representing both genders (n = 38 males and n = 54 females). Total 25(OH)D concentrations were determined using an immunoassay method called CMIA. In addition, 25(OH)D3 and vitamin D2 levels in serum were measured using liquid chromatography-mass spectrometry (LC-MS). Free 25(OH)D was measured and calculated according to the Bikle method.
Results: Among the participants, 54% exhibited total 25(OH)D3 levels below 20 ng/mL. Those with total 25(OH)D3 concentrations of 20 ng/mL or higher had significantly elevated mean serum levels of 25(OH)D3 and free vitamin D compared to those with levels below 20 ng/mL (P < 0.001). In opposition, the mean concentration of 25(OH)D2 did not show significant variation based on the criteria for vitamin D sufficiency. Additionally, serum levels of 25(OH)D2 were consistent across individuals, regardless of their free vitamin D concentrations.
Conclusion: The mean concentrations of serum 25(OH)D3 measured by LC-MS and free vitamin D affects the total 25(OH)D3 concentration as calculated by an automated system and indicates vitamin D deficiency. The mean concentration of 25(OH)D2 in serum, however, didn't differ among individuals according to vitamin D deficiency criteria and concentration of free vitamin D, thus does not directly indicate vitamin D deficiency.

Keywords

D vitamini 25-Hidroksivitamin D2 25-Hidroksivitamin D3 serbest D vitamini

Ethical Statement

Biruni Üniversitesi Girişimsel Olmayan Etik Kurul tarafından onay alınmıştır. Etik Kurul onay formuda sisteme yüklenmiştir.

Project Number

Herhangi bir projeden destek alınmamıştır.

References

  • 1. Wang S. Epidemiology of vitamin D in health and disease. Nutr Res Rev. 2009;2(22):188-203
  • 2. Zelzer S, Prüller F, Curcic P, Sloup Z, Holter M, Herrmann M, et al. Vitamin D Metabolites and Clinical Outcome in Hospitalized COVID-19 Patients. Nutrients. 2021;7(13):
  • 3. Ramasamy I. Vitamin D Metabolism and Guidelines for Vitamin D Supplementation. Clin Biochem Rev. 2020;3(41):103-26
  • 4. Nikolac Gabaj N, Unic A, Miler M, Pavicic T, Culej J, Bolanca I, et al. In sickness and in health: pivotal role of vitamin D. Biochem Med (Zagreb). 2020;2(30):020501
  • 5. Al-Thagfan, S S, Alolayan SO, Ahmed S, Emara M M, Awadallah MF, et al. Impacts of deficiency in vitamin D derivatives on disease severity in adult bronchial asthma patients. Pulm Pharmacol Ther. 2021;70):102073
  • 6. Jenkinson C. The vitamin D metabolome: An update on analysis and function. Cell Biochem Funct. 2019;6(37):408-23
  • 7. Bikle D. Vitamin D: production, metabolism and mechanisms of action. Europe PMC; 2015.
  • 8. Haussler MR., Whitfield GK, Kaneko I, Haussle CA, Hsieh D, Hsieh JC, t al. Molecular mechanisms of vitamin D action. Calcif Tissue Int. 2013;2(92):77-98
  • 9. Amrein K, Scherkl M, Hoffmann M, Neuwersch-Sommeregger S, Köstenberger M, Tmava Berisha A, et al. Vitamin D deficiency 2.0: an update on the current status worldwide. Eur J Clin Nutr. 2020;11(74):1498-513
  • 10. Glendenning P, Chew GT, Inderjeeth CA, Taranto M, Fraser WD, et al. Calculated free and bioavailable vitamin D metabolite concentrations in vitamin D-deficient hip fracture patients after supplementation with cholecalciferol and ergocalciferol. Bone. 2013;2(56):271-5
  • 11. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney, R. P., ... & Weaver, C. M. ( et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;7(96):1911-30
  • 12. Holick MF, Biancuzzo RM, Chen TC, Klein EK., Young A, Bibuld D, et al. Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D. J Clin Endocrinol Metab. 2008;3(93):677-81
  • 13. Shieh A, Chun RF, Ma C, Witzel S, Meyer B, Rafison B, et al. Effects of High-Dose Vitamin D2 Versus D3 on Total and Free 25-Hydroxyvitamin D and Markers of Calcium Balance. J Clin Endocrinol Metab. 2016;8(101):3070-8
  • 14. Romagnoli E, Mascia ML, Cipriani C, Fassino V, Mazzei F, D’Erasmo E., ... et al. Short and long-term variations in serum calciotropic hormones after a single very large dose of ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) in the elderly. J Clin Endocrinol Metab. 2008;8(93):3015-20
  • 15. Vieth R, Chan PC, MacFarlane GD. Efficacy and safety of vitamin D3 intake exceeding the lowest observed adverse effect level. Am J Clin Nutr. 2001;2(73):288-94
  • 16. Karcıoğlu Batur L, Özaydın A, Maviş ME, Gürsu GG, Harbige L, Hekim N.. Vitamin-D Binding Protein Gene Polymorphisms and Serum 25-Hydroxyvitamin-D in a Turkish Population. Metabolites. 2021;10(11):
  • 17. Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, Clinton SK, et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab. 2011;1(96):53-8
  • 18. A M Mondul, S J Weinstein, J Virtamo & D Albanes . Influence of vitamin D binding protein on the association between circulating vitamin D and risk of bladder cancer. Br J Cancer. 2012;9(107):1589-94
  • 19. Powe CE, Ricciardi C, Berg AH, Erdenesanaa D, Collerone G, Ankers E, et al. Vitamin D-binding protein modifies the vitamin D-bone mineral density relationship. J Bone Miner Res. 2011;7(26):1609-16
  • 20. Galior K, Ketha H, Grebe S, Singh RJ, et al. 10 years of 25-hydroxyvitamin-D testing by LC-MS/MS-trends in vitamin-D deficiency and sufficiency. Bone Rep. 2018;8):268-73
  • 21. Ferrari D, Lombardi G, Banfi G,. Concerning the vitamin D reference range: pre-analytical and analytical variability of vitamin D measurement. Biochem Med (Zagreb). 2017;3(27):030501
  • 22. Stepman HC, Vanderroost A, Van Uytfanghe K, & Thienpont LM, et al. Candidate reference measurement procedures for serum 25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 by using isotope-dilution liquid chromatography-tandem mass spectrometry. Clin Chem. 2011;3(57):441-8
  • 23. Tripkovic L, Wilson LR, Hart K, Johnsen S, De Lusignan S, Smith CP, et al. Daily supplementation with 15 mug vitamin D(2) compared with vitamin D(3) to increase wintertime 25-hydroxyvitamin D status in healthy South Asian and white European women: a 12-wk randomized, placebo-controlled food-fortification trial. Am J Clin Nutr. 2017;2(106):481-90
  • 24. Tripkovic L, Lambert H, Hart K, Smith CP, Bucca G, Penson S, . et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr. 2012;6(95):1357-64
  • 25. Heaney RP, Recker RR, Grote J, Horst RL, Armas L, A et al. Vitamin D(3) is more potent than vitamin D(2) in humans. J Clin Endocrinol Metab. 2011;3(96):E447-52
  • 26. Horst R, Prapong S, Reinhardt T, Koszewski N, Knutson J, Bishop C.Comparison of the relative effects of 1,24-dihydroxyvitamin D(2) [1, 24-(OH)(2)D(2)], 1,24-dihydroxyvitamin D(3) [1,24-(OH)(2)D(3)], and 1,25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)] on selected vitamin D-regulated events in the rat. Biochem Pharmacol. 2000;5(60):701-8
  • 27. Zhu T, Zhao J, Zhuo S, Hu Z, Ouyang S, Wunier Y,. et al. High Fat Diet and High Cholesterol Diet Reduce Hepatic Vitamin D‐25‐Hydroxylase Expression and Serum 25‐Hydroxyvitamin D3 Level through Elevating Circulating Cholesterol, Glucose, and Insulin Levels. Mol Nutr Food Res. 2021;65(21):2100220.
  • 28. Hanel A, Veldhuizen C, Carlberg C,. Gene-regulatory potential of 25-hydroxyvitamin D3 and D2. Front Nutr. 2022;9:910601.
  • 29. Hasan M, Oster M, Reyer H, Wimmers K, Fischer DC,. Efficacy of dietary vitamin D3 and 25 (OH) D3 on reproductive capacities, growth performance, immunity and bone development in pigs. Br J Nutr. 2023;130(8):1298-307.
  • 30. Houghton LA, Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. Am J Clin Nutr. 2006;4(84):694-7
  • 31. Sanghera DK, Sapkota BR, Aston CE, Blackett PR. Vitamin D Status, Gender Differences, and Cardiometabolic Health Disparities. Ann Nutr Metab. 2017;2(70):79-87
  • 32. Johnson LK, Hofsø D, Aasheim ET, Tanbo T, Holven KB, Andersen LF, et al. Impact of gender on vitamin D deficiency in morbidly obese patients: a cross-sectional study. Eur J Clin Nutr. 2012;1(66):83-90
  • 33. Abudawood M, Tabassum H, Ansar S, Almosa K, Sobki S, Ali MN, et al. Assessment of gender-related differences in vitamin D levels and cardiovascular risk factors in Saudi patients with type 2 diabetes mellitus. Saudi J Biol Sci. 2018;1(25):31-36

D Vitamini Yetersizliğinin Biyobelirteçleri: Sağlıklı Türk bireylerde D vitamini Metabolit Düzeyleri 25-Hidroksivitamin D2 düzeylerine bağlı değildir

Year 2025, Volume: 17 Issue: 1, 84 - 90, 27.03.2025

Cüneyd Yavaş , Nezih Hekim , Lütfiye Karcıoğlu Batur , Recep Eröz , Ahmet Özaydın

Abstract

Amaç: Hastaya özgü faktörler yeterlilik için gerekli ek D vitamini dozunu etkileyebilir ve D vitamini takviyesi reçete etmek için hangi metabolitin klinik olarak anlamlı kabul edildiğini doğrulamak önemlidir. Bu çalışmada, sağlıklı bir Türk popülasyonunda 25(OH)D2 ve serbest D vitamini düzeyleri ile D vitamini eksikliği arasındaki ilişki değerlendirilmiştir.
Yöntem: Her iki cinsiyeti temsil eden 18 yaş üstü 92 sağlıklı yetişkinden kan örnekleri alınmıştır (n = 38 erkek ve n = 54 kadın). Toplam 25(OH)D konsantrasyonları CMIA adı verilen bir immünoassay yöntemi kullanılarak belirlenmiştir. Ayrıca, serumdaki 25(OH)D3 ve D2 vitamini seviyeleri sıvı kromatografi-kütle spektrometresi (LC-MS) kullanılarak ölçülmüştür. Serbest 25(OH)D hesaplaması Bikle yöntemine göre yapılmıştır.
Bulgular: Total 25(OH)D3 düzeyi ölçülen katılımcıların %54'ünde 20 ng/mL'nin altındaydı. Toplam 25(OH)D3 konsantrasyonu 20 ng/mL veya daha yüksek olanların ortalama serum 25(OH)D3 ve serbest D vitamini ölçüm seviyeleri 20 ng/mL'nin altında olanlara kıyasla anlamlı derecede yüksekti (P < 0.001). Buna karşılık, ortalama 25(OH)D2 konsantrasyonu D vitamini eksikliği kriterlerine göre önemli bir değişiklik göstermemiştir. Ayrıca, 25(OH)D2 serum seviyeleri, serbest D vitamini konsantrasyonlarından bağımsız olarak bireyler arasında tutarlıydı.
Sonuç: LC-MS ile ölçülen ortalama serum 25(OH)D3 ve serbest D vitamini konsantrasyonları, otomatik bir sistemle ölçülen toplam 25(OH)D3 konsantrasyonunu etkiler ve D vitamini eksikliğini gösterir. Bununla birlikte, serumdaki ortalama 25(OH)D2 konsantrasyonu, D vitamini eksikliği kriterlerine ve serbest D vitamini konsantrasyonuna göre bireyler arasında farklılık göstermemiştir, bu nedenle doğrudan D vitamini eksikliğini göstermez.

Keywords

D vitamini 25-Hidroksivitamin D2 25-Hidroksivitamin D3 serbest D vitamini

Project Number

Herhangi bir projeden destek alınmamıştır.

References

  • 1. Wang S. Epidemiology of vitamin D in health and disease. Nutr Res Rev. 2009;2(22):188-203
  • 2. Zelzer S, Prüller F, Curcic P, Sloup Z, Holter M, Herrmann M, et al. Vitamin D Metabolites and Clinical Outcome in Hospitalized COVID-19 Patients. Nutrients. 2021;7(13):
  • 3. Ramasamy I. Vitamin D Metabolism and Guidelines for Vitamin D Supplementation. Clin Biochem Rev. 2020;3(41):103-26
  • 4. Nikolac Gabaj N, Unic A, Miler M, Pavicic T, Culej J, Bolanca I, et al. In sickness and in health: pivotal role of vitamin D. Biochem Med (Zagreb). 2020;2(30):020501
  • 5. Al-Thagfan, S S, Alolayan SO, Ahmed S, Emara M M, Awadallah MF, et al. Impacts of deficiency in vitamin D derivatives on disease severity in adult bronchial asthma patients. Pulm Pharmacol Ther. 2021;70):102073
  • 6. Jenkinson C. The vitamin D metabolome: An update on analysis and function. Cell Biochem Funct. 2019;6(37):408-23
  • 7. Bikle D. Vitamin D: production, metabolism and mechanisms of action. Europe PMC; 2015.
  • 8. Haussler MR., Whitfield GK, Kaneko I, Haussle CA, Hsieh D, Hsieh JC, t al. Molecular mechanisms of vitamin D action. Calcif Tissue Int. 2013;2(92):77-98
  • 9. Amrein K, Scherkl M, Hoffmann M, Neuwersch-Sommeregger S, Köstenberger M, Tmava Berisha A, et al. Vitamin D deficiency 2.0: an update on the current status worldwide. Eur J Clin Nutr. 2020;11(74):1498-513
  • 10. Glendenning P, Chew GT, Inderjeeth CA, Taranto M, Fraser WD, et al. Calculated free and bioavailable vitamin D metabolite concentrations in vitamin D-deficient hip fracture patients after supplementation with cholecalciferol and ergocalciferol. Bone. 2013;2(56):271-5
  • 11. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney, R. P., ... & Weaver, C. M. ( et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;7(96):1911-30
  • 12. Holick MF, Biancuzzo RM, Chen TC, Klein EK., Young A, Bibuld D, et al. Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D. J Clin Endocrinol Metab. 2008;3(93):677-81
  • 13. Shieh A, Chun RF, Ma C, Witzel S, Meyer B, Rafison B, et al. Effects of High-Dose Vitamin D2 Versus D3 on Total and Free 25-Hydroxyvitamin D and Markers of Calcium Balance. J Clin Endocrinol Metab. 2016;8(101):3070-8
  • 14. Romagnoli E, Mascia ML, Cipriani C, Fassino V, Mazzei F, D’Erasmo E., ... et al. Short and long-term variations in serum calciotropic hormones after a single very large dose of ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) in the elderly. J Clin Endocrinol Metab. 2008;8(93):3015-20
  • 15. Vieth R, Chan PC, MacFarlane GD. Efficacy and safety of vitamin D3 intake exceeding the lowest observed adverse effect level. Am J Clin Nutr. 2001;2(73):288-94
  • 16. Karcıoğlu Batur L, Özaydın A, Maviş ME, Gürsu GG, Harbige L, Hekim N.. Vitamin-D Binding Protein Gene Polymorphisms and Serum 25-Hydroxyvitamin-D in a Turkish Population. Metabolites. 2021;10(11):
  • 17. Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, Clinton SK, et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab. 2011;1(96):53-8
  • 18. A M Mondul, S J Weinstein, J Virtamo & D Albanes . Influence of vitamin D binding protein on the association between circulating vitamin D and risk of bladder cancer. Br J Cancer. 2012;9(107):1589-94
  • 19. Powe CE, Ricciardi C, Berg AH, Erdenesanaa D, Collerone G, Ankers E, et al. Vitamin D-binding protein modifies the vitamin D-bone mineral density relationship. J Bone Miner Res. 2011;7(26):1609-16
  • 20. Galior K, Ketha H, Grebe S, Singh RJ, et al. 10 years of 25-hydroxyvitamin-D testing by LC-MS/MS-trends in vitamin-D deficiency and sufficiency. Bone Rep. 2018;8):268-73
  • 21. Ferrari D, Lombardi G, Banfi G,. Concerning the vitamin D reference range: pre-analytical and analytical variability of vitamin D measurement. Biochem Med (Zagreb). 2017;3(27):030501
  • 22. Stepman HC, Vanderroost A, Van Uytfanghe K, & Thienpont LM, et al. Candidate reference measurement procedures for serum 25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 by using isotope-dilution liquid chromatography-tandem mass spectrometry. Clin Chem. 2011;3(57):441-8
  • 23. Tripkovic L, Wilson LR, Hart K, Johnsen S, De Lusignan S, Smith CP, et al. Daily supplementation with 15 mug vitamin D(2) compared with vitamin D(3) to increase wintertime 25-hydroxyvitamin D status in healthy South Asian and white European women: a 12-wk randomized, placebo-controlled food-fortification trial. Am J Clin Nutr. 2017;2(106):481-90
  • 24. Tripkovic L, Lambert H, Hart K, Smith CP, Bucca G, Penson S, . et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr. 2012;6(95):1357-64
  • 25. Heaney RP, Recker RR, Grote J, Horst RL, Armas L, A et al. Vitamin D(3) is more potent than vitamin D(2) in humans. J Clin Endocrinol Metab. 2011;3(96):E447-52
  • 26. Horst R, Prapong S, Reinhardt T, Koszewski N, Knutson J, Bishop C.Comparison of the relative effects of 1,24-dihydroxyvitamin D(2) [1, 24-(OH)(2)D(2)], 1,24-dihydroxyvitamin D(3) [1,24-(OH)(2)D(3)], and 1,25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)] on selected vitamin D-regulated events in the rat. Biochem Pharmacol. 2000;5(60):701-8
  • 27. Zhu T, Zhao J, Zhuo S, Hu Z, Ouyang S, Wunier Y,. et al. High Fat Diet and High Cholesterol Diet Reduce Hepatic Vitamin D‐25‐Hydroxylase Expression and Serum 25‐Hydroxyvitamin D3 Level through Elevating Circulating Cholesterol, Glucose, and Insulin Levels. Mol Nutr Food Res. 2021;65(21):2100220.
  • 28. Hanel A, Veldhuizen C, Carlberg C,. Gene-regulatory potential of 25-hydroxyvitamin D3 and D2. Front Nutr. 2022;9:910601.
  • 29. Hasan M, Oster M, Reyer H, Wimmers K, Fischer DC,. Efficacy of dietary vitamin D3 and 25 (OH) D3 on reproductive capacities, growth performance, immunity and bone development in pigs. Br J Nutr. 2023;130(8):1298-307.
  • 30. Houghton LA, Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. Am J Clin Nutr. 2006;4(84):694-7
  • 31. Sanghera DK, Sapkota BR, Aston CE, Blackett PR. Vitamin D Status, Gender Differences, and Cardiometabolic Health Disparities. Ann Nutr Metab. 2017;2(70):79-87
  • 32. Johnson LK, Hofsø D, Aasheim ET, Tanbo T, Holven KB, Andersen LF, et al. Impact of gender on vitamin D deficiency in morbidly obese patients: a cross-sectional study. Eur J Clin Nutr. 2012;1(66):83-90
  • 33. Abudawood M, Tabassum H, Ansar S, Almosa K, Sobki S, Ali MN, et al. Assessment of gender-related differences in vitamin D levels and cardiovascular risk factors in Saudi patients with type 2 diabetes mellitus. Saudi J Biol Sci. 2018;1(25):31-36
There are 33 citations in total.

Details

Primary Language English
Subjects Health Services and Systems (Other)
Journal Section Articles
Authors

Cüneyd Yavaş 0000-0002-1597-5922

Nezih Hekim 0000-0003-2613-8676

Lütfiye Karcıoğlu Batur 0000-0002-4803-9137

Recep Eröz 0000-0003-0840-2613

Ahmet Özaydın 0000-0003-3959-3053

Project Number Herhangi bir projeden destek alınmamıştır.
Publication Date March 27, 2025
Submission Date October 3, 2024
Acceptance Date March 23, 2025
Published in Issue Year 2025 Volume: 17 Issue: 1

Cite

APA Yavaş, C., Hekim, N., Karcıoğlu Batur, L., Eröz, R., et al. (2025). Biomarkers of Vitamin D Sufficiency: Vitamin D metabolite levels do not depend on 25-Hydroxyvitamin D2 levels in healthy Turkish individuals. Konuralp Medical Journal, 17(1), 84-90. https://doi.org/10.18521/ktd.1560608
AMA Yavaş C, Hekim N, Karcıoğlu Batur L, Eröz R, Özaydın A. Biomarkers of Vitamin D Sufficiency: Vitamin D metabolite levels do not depend on 25-Hydroxyvitamin D2 levels in healthy Turkish individuals. Konuralp Medical Journal. March 2025;17(1):84-90. doi:10.18521/ktd.1560608
Chicago Yavaş, Cüneyd, Nezih Hekim, Lütfiye Karcıoğlu Batur, Recep Eröz, and Ahmet Özaydın. “Biomarkers of Vitamin D Sufficiency: Vitamin D Metabolite Levels Do Not Depend on 25-Hydroxyvitamin D2 Levels in Healthy Turkish Individuals”. Konuralp Medical Journal 17, no. 1 (March 2025): 84-90. https://doi.org/10.18521/ktd.1560608.
EndNote Yavaş C, Hekim N, Karcıoğlu Batur L, Eröz R, Özaydın A (March 1, 2025) Biomarkers of Vitamin D Sufficiency: Vitamin D metabolite levels do not depend on 25-Hydroxyvitamin D2 levels in healthy Turkish individuals. Konuralp Medical Journal 17 1 84–90.
IEEE C. Yavaş, N. Hekim, L. Karcıoğlu Batur, R. Eröz, and A. Özaydın, “Biomarkers of Vitamin D Sufficiency: Vitamin D metabolite levels do not depend on 25-Hydroxyvitamin D2 levels in healthy Turkish individuals”, Konuralp Medical Journal, vol. 17, no. 1, pp. 84–90, 2025, doi: 10.18521/ktd.1560608.
ISNAD Yavaş, Cüneyd et al. “Biomarkers of Vitamin D Sufficiency: Vitamin D Metabolite Levels Do Not Depend on 25-Hydroxyvitamin D2 Levels in Healthy Turkish Individuals”. Konuralp Medical Journal 17/1 (March 2025), 84-90. https://doi.org/10.18521/ktd.1560608.
JAMA Yavaş C, Hekim N, Karcıoğlu Batur L, Eröz R, Özaydın A. Biomarkers of Vitamin D Sufficiency: Vitamin D metabolite levels do not depend on 25-Hydroxyvitamin D2 levels in healthy Turkish individuals. Konuralp Medical Journal. 2025;17:84–90.
MLA Yavaş, Cüneyd et al. “Biomarkers of Vitamin D Sufficiency: Vitamin D Metabolite Levels Do Not Depend on 25-Hydroxyvitamin D2 Levels in Healthy Turkish Individuals”. Konuralp Medical Journal, vol. 17, no. 1, 2025, pp. 84-90, doi:10.18521/ktd.1560608.
Vancouver Yavaş C, Hekim N, Karcıoğlu Batur L, Eröz R, Özaydın A. Biomarkers of Vitamin D Sufficiency: Vitamin D metabolite levels do not depend on 25-Hydroxyvitamin D2 levels in healthy Turkish individuals. Konuralp Medical Journal. 2025;17(1):84-90.
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