VDR rs731235: What Your TaqI Genotype Means
The rs731235 variant (often cross-referenced with rs731236) is a well-known single nucleotide polymorphism historically designated as the TaqI restriction site within exon 9 of the vitamin D receptor (VDR) gene. It has been examined in candidate-gene studies for potential associations with vitamin D metabolism, ovarian follicular development, and susceptibility to conditions like polycystic ovary syndrome (PCOS). However, overall clinical evidence remains limited and heterogeneous across diverse global cohorts.
What each genotype means
Typical VDR expression profile
You carry two copies of the common T allele (historically designated as the 'T' allele in TaqI restriction digest assays). In research evaluating the VDR TaqI polymorphism, this genotype is generally considered the baseline profile, though studies examining its relationship to follicular development, polycystic ovary syndrome (PCOS), and vitamin D metabolism show limited and conflicting evidence. These findings represent subtle statistical variations in population cohorts rather than a diagnosis or direct clinical indicator.
Carried by roughly 35% to 40% of individuals of European descent and over 75% to 80% of individuals of East Asian ancestry.
Intermediate VDR receptor profile
You carry one copy of the C allele and one copy of the T allele (often noted as the 'Tt' genotype in traditional TaqI literature). While some candidate gene studies suggest this genotype may weakly influence follicular development and PCOS susceptibility, broad meta-analyses show mixed or inconclusive results across different ancestral populations. Carrying this genotype does not cause any endocrine condition and should be viewed solely as common, neutral genetic variation.
Carried by approximately 45% to 50% of individuals of European ancestry and roughly 15% to 20% of individuals in East Asian populations.
Alternative VDR receptor profile
You carry two copies of the C allele (historically referred to as the homozygous 'tt' genotype in TaqI digest nomenclature). Some small-scale studies have explored whether this profile alters vitamin D receptor signaling, follicular maturation, or susceptibility to polycystic ovary syndrome, but overall scientific evidence remains limited and conflicting. This result does not indicate any medical diagnosis or hormone imbalance, but rather reflects normal biological variation.
Carried by approximately 15% to 18% of individuals of European descent, while being relatively uncommon in East Asian populations (under 2%).
Understanding the Variant: VDR TaqI
The single nucleotide polymorphism rs731235 is located on chromosome 12 inside exon 9 of the VDR gene. In standard genomic reference transcripts, it represents a synonymous variant where a cytosine (C) replaces a thymine (T), often mapped complementarily as A/G depending on the strand. In classic molecular biology, it is referred to as the TaqI restriction fragment length polymorphism because the alteration alters the recognition sequence for the TaqI endonuclease. Historically, geneticists designated the presence of the restriction site as lowercase 't' and the absence of the site as uppercase 'T'. Because this change does not alter the amino acid sequence of the final receptor protein, researchers hypothesize that its potential biological impact stems from altering mRNA stability, translation kinetics, or linkage disequilibrium with other regulatory variants situated nearby in the 3' untranslated region.
Biological Role of the Vitamin D Receptor
The VDR gene encodes the vitamin D receptor, an essential nuclear transcription factor that mediates the biological effects of calcitriol, the active hormonal form of vitamin D. When activated, the receptor forms a heterodimer with the retinoid X receptor (RXR), translocating to the nucleus to bind vitamin D response elements (VDREs) across hundreds of human genes. Beyond its classic role in calcium absorption, phosphate balance, and bone mineral homeostasis, the VDR is broadly expressed throughout human tissues, including pancreatic beta cells, immune cells, and ovarian granulosa cells. Through these varied tissue pathways, VDR signaling modulates local steroidogenesis, follicular recruitment, insulin sensitivity, and inflammatory cytokine pathways, which has made it a frequent candidate gene in metabolic and reproductive health research.
Research Associations: Metabolic Traits and PCOS
A broad body of candidate gene literature has examined rs731235 for associations with endocrine conditions, notably polycystic ovary syndrome (PCOS). Several small-scale case-control studies have reported modest statistical associations between specific TaqI alleles and altered risk of PCOS, abnormal follicular maturation, or variation in circulating androgens and insulin resistance markers. Beyond reproductive traits, investigators have examined rs731235 in relation to bone mineral density, diabetic nephropathy, and general metabolic parameters. Nevertheless, large-scale genome-wide association studies (GWAS) frequently fail to replicate these findings at rigorous statistical significance thresholds. Because many published positive associations stem from small, single-ancestry cohorts with mixed definitions of risk alleles, the current scientific evidence linking rs731235 to complex disease phenotypes is classified as limited and preliminary.
Population Distribution and Global Variation
The distribution of alleles at the VDR TaqI locus varies markedly across world ancestries. According to global genomic reference resources such as gnomAD and 1000 Genomes, the minor allele frequency is substantial in European cohorts, typically hovering around 0.40. In contrast, it occurs far less frequently among East Asian populations, where the minor allele frequency drops to roughly 0.10. Intermediate to diverse frequencies are seen in Middle Eastern, South Asian, and African populations. This notable geographic divergence means that baseline genotype frequencies differ significantly by ethnic background, underscoring why candidate gene association findings in one population cannot be reliably generalized to individuals from different ancestral backgrounds.
What You Can and Cannot Do With This Result
It is critical to recognize that rs731235 is not a diagnostic marker. Carrying one or two copies of a statistically associated allele does not mean you have or will develop PCOS, metabolic complications, or vitamin D deficiency, nor does a protective genotype guarantee immunity. Complex endocrine and metabolic conditions are polygenic, shaped by hundreds of genetic loci alongside environmental factors including diet, sunlight exposure, physical activity, and overall health status. This genetic finding should never be used to initiate self-treatment or take high-dose nutritional supplements without clinical supervision. If you have questions regarding your vitamin D levels, hormonal health, or reproductive wellness, consult a qualified healthcare provider who can evaluate standard laboratory tests.
How common is this variant?
The minor allele frequency for rs731235 is approximately 0.40 in populations of European ancestry, whereas it is significantly lower in East Asian populations at around 0.10.
Frequently asked questions
Does my VDR TaqI genotype mean I have PCOS?
No. Polycystic ovary syndrome is a complex medical condition diagnosed using established clinical criteria such as irregular ovulatory cycles, physical or biochemical signs of hyperandrogenism, and ultrasound imaging of the ovaries. The rs731235 variant has only shown weak statistical associations in research cohorts and cannot diagnose, predict, or rule out PCOS.
Should I take extra vitamin D if I carry the variant allele?
You should not alter your supplement intake based solely on this genotype. While VDR is involved in how cells respond to vitamin D, nutritional status is properly evaluated through routine clinical blood tests like 25-hydroxyvitamin D. Always discuss any dietary changes or high-dose supplementation with your healthcare provider.
Why is this variant sometimes called TaqI or written with different letters?
Historically, geneticists identified this variant using restriction enzymes, naming it after the TaqI restriction endonuclease and designating genotypes with letters like 'T' and 't'. Modern sequencing tools report exact base changes like C and T, and depending on whether the forward or reverse genomic strand is analyzed, it may also appear documented as G or A.
Can this genetic variant affect my medication response?
There are currently no established pharmacogenomic guidelines from standard bodies like CPIC or PharmGKB recommending medication or dosing adjustments based on rs731235. If you take medications related to metabolic or reproductive health, any adjustments must be managed directly by your physician or pharmacist.
Sources & further reading
Educational information only, last refreshed 9/14/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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