Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 4 complete abstracts (694 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
The physiologically active form of vitamin D. It is formed primarily in the kidney by enzymatic hydroxylation of 25-hydroxycholecalciferol (calcifediol). Its production is stimulated by low blood calcium levels and parathyroid hormone. Calcitriol increases intestinal absorption of calcium and phosphorus, and in concert with parathyroid hormone increases bone resorption.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: 1,25(OH)2D3; 1 alpha,25-Dihydroxycholecalciferol; 1 alpha,25-Dihydroxyvitamin D3; 1 alpha,25 Dihydroxyvitamin D3; D3, 1 alpha,25-Dihydroxyvitamin; 1,25-Dihydroxycholecalciferol; 1,25 Dihydroxycholecalciferol; 1,25-Dihydroxyvitamin D3.
Where it fits in the MeSH classification
- Broader topics
- Dihydroxycholecalciferols
- See also
- Receptors, Calcitriol
Related concepts
- Calcifediol
Research landscape
PubMed indexes 15,279 records tagged with the MeSH heading “Calcitriol” (counts retrieved 2026-10-31). 1,126 of them (7.4%) were published from 2020 onward, and the busiest period so far is through 1999 with 7,816 records.
Reviews account for 1,657 records (10.8%) and meta-analyses for 47. Randomized controlled trials number 696 (4.6%) as a share of all records on the topic.
Show the data
| Period | Records |
|---|---|
| through 1999 | 7,816 |
| 2000-2009 | 3,518 |
| 2010-2019 | 2,819 |
| 2020 onward | 1,126 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 1,657 | 10.8% |
| Meta-analyses | 47 | 0.3% |
| Randomized controlled trials | 696 | 4.6% |
Method: PubMed query "Calcitriol"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in drugs and chemicals
Studies of a chemical or drug can answer very different questions: what it is and how it behaves in cells and animals, how the body handles it, and whether it changes outcomes in people. Laboratory and animal findings often do not carry over to patients, and observational studies of exposures are confounded by who uses a substance and why. Nothing on this page is a recommendation to use, avoid, start or stop any substance or medicine; talk to a qualified clinician or pharmacist about your own situation. Check the dose, the species, the comparison group and whether a patient-relevant outcome was measured.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| Vitamin D metabolites and the gut microbiome in older men | 2020 | Research article Design not recorded in structured metadata | 132 | cc by PMID 33244003 · DOI · PMC7693238 |
| Vitamin D exposure and Risk of Breast Cancer: a meta-analysis | 2018 | Meta-analysis Design not recorded in structured metadata | 91 | cc by PMID 29899554 · DOI · PMC5997996 |
| Vitamin D, Skeletal Muscle Function and Athletic Performance in Athletes-A Narrative Review | 2019 | Review article Design not recorded in structured metadata | 90 | cc by PMID 31382666 · DOI · PMC6722905 |
| Regulation of Renal and Extrarenal Calcitriol Synthesis and Its Clinical Implications | 2025 | Review article Design not recorded in structured metadata | 7 | cc by PMID 40565034 · DOI · PMC12192668 |
Vitamin D metabolites and the gut microbiome in older men [1]
Abstract reading summary — source excerpts
- Opening excerpt
- The vitamin D receptor is highly expressed in the gastrointestinal tract where it transacts gene expression.
- Closing excerpt
- Men with higher levels of 1,25(OH)2D and higher activation ratios, but not 25(OH)D itself, are more likely to possess butyrate producing bacteria that are associated with better gut microbial health.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (149 words)
The vitamin D receptor is highly expressed in the gastrointestinal tract where it transacts gene expression. With current limited understanding of the interactions between the gut microbiome and vitamin D, we conduct a cross-sectional analysis of 567 older men quantifying serum vitamin D metabolites using LC-MSMS and defining stool sub-Operational Taxonomic Units from16S ribosomal RNA gene sequencing data. Faith's Phylogenetic Diversity and non-redundant covariate analyses reveal that the serum 1,25(OH)2D level explains 5% of variance in α-diversity. In β-diversity analyses using unweighted UniFrac, 1,25(OH)2D is the strongest factor assessed, explaining 2% of variance. Random forest analyses identify 12 taxa, 11 in the phylum Firmicutes, eight of which are positively associated with either 1,25(OH)2D and/or the hormone-to-prohormone [1,25(OH)2D/25(OH)D] "activation ratio." Men with higher levels of 1,25(OH)2D and higher activation ratios, but not 25(OH)D itself, are more likely to possess butyrate producing bacteria that are associated with better gut microbial health.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 33244003 · DOI · PMC7693238
Vitamin D exposure and Risk of Breast Cancer: a meta-analysis [2]
Abstract reading summary — source excerpts
- Opening excerpt
- The relationship between vitamin D and breast cancer is still controversial.
- Closing excerpt
- ConclusionThis systematic review suggests a protective relationship between circulating vitamin D (measured as 25(OH) D) and breast cancer development in premenopausal women.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (199 words)
The relationship between vitamin D and breast cancer is still controversial. The present meta-analysis examines the effects of the 25(OH)D, 1,25(OH)2D and vitamin D intake on breast cancer risk. For this purpose, a PubMed, Scopus and Web of Science-databases search was conducted including all papers published with the keywords "breast cancer" and "vitamin D" with at least one reported relative risk (RR) or odds ratio (OR). In total sixty eight studies published between 1998 and 2018 were analyzed. Information about type of study, hormonal receptors and menopausal status was retrieved. Pooled OR or RR were estimated by weighting individual OR/RR by the inverse of their variance Our study showed a protective effect between 25 (OH) D and breast cancer in both cohort studies (RR = 0.85, 95%CI:0.74-0.98) and case-control studies (OR = 0.65, 95%CI: 0.56-0.76). However, analyzing by menopausal status, the protective vitamin D - breast cancer association persisted only in the premenopausal group (OR = 0.67, 95%CI: 0.49-0.92) when restricting the analysis to nested case-control studies. No significant association was found for vitamin D intake or 1,25(OH)2D.ConclusionThis systematic review suggests a protective relationship between circulating vitamin D (measured as 25(OH) D) and breast cancer development in premenopausal women.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 29899554 · DOI · PMC5997996
Vitamin D, Skeletal Muscle Function and Athletic Performance in Athletes-A Narrative Review [3]
Abstract reading summary — source excerpts
- Opening excerpt
- The active form of vitamin D (calcitriol) exerts its biological effects by binding to nuclear vitamin D receptors (VDRs), which are found in most human extraskeletal cells, including skeletal muscles.
- Closing excerpt
- Further studies are necessary to fully characterize the underlying mechanisms of calcitriol action in the human skeletal muscle tissue, and to understand how these actions impact the athletic performance in athletes.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (146 words)
The active form of vitamin D (calcitriol) exerts its biological effects by binding to nuclear vitamin D receptors (VDRs), which are found in most human extraskeletal cells, including skeletal muscles. Vitamin D deficiency may cause deficits in strength, and lead to fatty degeneration of type II muscle fibers, which has been found to negatively correlate with physical performance. Vitamin D supplementation has been shown to improve vitamin D status and can positively affect skeletal muscles. The purpose of this study is to summarize the current evidence of the relationship between vitamin D, skeletal muscle function and physical performance in athletes. Additionally, we will discuss the effect of vitamin D supplementation on athletic performance in players. Further studies are necessary to fully characterize the underlying mechanisms of calcitriol action in the human skeletal muscle tissue, and to understand how these actions impact the athletic performance in athletes.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 31382666 · DOI · PMC6722905
Regulation of Renal and Extrarenal Calcitriol Synthesis and Its Clinical Implications [4]
Abstract reading summary — source excerpts
- Opening excerpt
- There is evidence that calcitriol is the only biologically active vitamin D metabolite.
- Closing excerpt
- Since various factors can differently influence calcitriol regulation, more personalized preventive/therapeutic strategies of targeting calcitriol synthesis are necessary.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (200 words)
There is evidence that calcitriol is the only biologically active vitamin D metabolite. This review summarizes data on the regulation of renal and extrarenal synthesis of calcitriol by nutritional, physiologic, mechanical, genetic, and disease-related factors. Relatively low circulating calcitriol due to low substrate availability, i.e., low circulating 25-hydroxyvitamin D, has been reported in nutritional rickets, osteomalacia, obesity, and preeclampsia. In these situations, vitamin D supplementation can increase circulating calcitriol and, together with calcium, prevent rickets/osteomalacia and reduce the risk of preeclampsia and obesity-related type 2 diabetes mellitus. However, the correction of low circulating calcitriol due to mechanical unloading/immobilization by vitamin D supplementation is not effective in preventing osteoporotic fractures. Circulating calcitriol is also low in diseases such as cardiac and renal failure. Both illnesses share some other similarities regarding dysregulated calcium/phosphate metabolism, including elevated parathyroid hormone and fibroblast growth factor-23, suggesting similar treatment strategies. Genetic disorders of vitamin D metabolism are rare and can affect circulating calcitriol differently. Calcitriol synthesis in immune cells is obviously not primarily dependent on circulating 25-hydroxyvitamin D, which challenges the use of vitamin D for infection prevention. Since various factors can differently influence calcitriol regulation, more personalized preventive/therapeutic strategies of targeting calcitriol synthesis are necessary.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40565034 · DOI · PMC12192668
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article The nuclear vitamin D receptor: biological and molecular regulatory properties revealed [5]
- Research article New clues about vitamin D functions in the nervous system [6]
- Research article Vitamin D receptor (VDR)-mediated actions of 1α,25(OH)₂vitamin D₃: genomic and non-genomic mechanisms [7]
- Research article Regulation of phosphate homeostasis by PTH, vitamin D, and FGF23 [8]
- Research article Vitamin D and diabetes [9]
- Research article Vitamin D: Classic and Novel Actions [10]
References
- Thomas RL, Jiang L, Adams JS, Xu ZZ, Shen J, Janssen S, et al.. Vitamin D metabolites and the gut microbiome in older men. . 2020. PMID 33244003 · DOI · PMC7693238
- Estébanez N, Gómez-Acebo I, Palazuelos C, Llorca J, Dierssen-Sotos T. Vitamin D exposure and Risk of Breast Cancer: a meta-analysis. . 2018. PMID 29899554 · DOI · PMC5997996
- Książek A, Zagrodna A, Słowińska-Lisowska M. Vitamin D, Skeletal Muscle Function and Athletic Performance in Athletes-A Narrative Review. . 2019. PMID 31382666 · DOI · PMC6722905
- Zittermann A. Regulation of Renal and Extrarenal Calcitriol Synthesis and Its Clinical Implications. . 2025. PMID 40565034 · DOI · PMC12192668
- Haussler MR, Whitfield GK, Haussler CA, Hsieh JC, Thompson PD, Selznick SH, et al.. The nuclear vitamin D receptor: biological and molecular regulatory properties revealed. J Bone Miner Res. 1998. PMID 9525333 · DOI
- Garcion E, Wion-Barbot N, Montero-Menei CN, Berger F, Wion D. New clues about vitamin D functions in the nervous system. Trends Endocrinol Metab. 2002. PMID 11893522 · DOI
- Haussler MR, Jurutka PW, Mizwicki M, Norman AW. Vitamin D receptor (VDR)-mediated actions of 1α,25(OH)₂vitamin D₃: genomic and non-genomic mechanisms. Best Pract Res Clin Endocrinol Metab. 2011. PMID 21872797 · DOI
- Bergwitz C, Jüppner H. Regulation of phosphate homeostasis by PTH, vitamin D, and FGF23. Annu Rev Med. 2010. PMID 20059333 · DOI · PMC4777331
- Mathieu C, Gysemans C, Giulietti A, Bouillon R. Vitamin D and diabetes. Diabetologia. 2005. PMID 15971062 · DOI
- Gil Á, Plaza-Diaz J, Mesa MD. Vitamin D: Classic and Novel Actions. Ann Nutr Metab. 2018. PMID 29346788 · DOI
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-31.
See how EvidenceLib is built. Spotted an error? Email support@evidencehelix.com.
Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.