What you carry at this position in your DNA and what research says about it.
Hormone and Drug Metabolism: 9/10 evidence, 56 publications.
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Sample genotype (not yours): G/G
Typical Hormone and Drug Metabolism
Standard enzyme function maintains typical baseline risks for hormone-related conditions and standard responses to medications.
What this genotype means: Standard estrogen processing; Typical response to chemotherapy; Baseline prostate cancer risk.
Sample genotype (not yours): C/C
Lower Prostate Cancer Risk with Mixed Drug Sensitivity
Two copies of the variant allele significantly lower prostate cancer risk but increase susceptibility to chemotherapy-induced nausea.
What this genotype means: Significantly lower risk of prostate cancer; Reduced risk of chemotherapy-induced neuropathy; Higher risk of chemotherapy-induced nausea.
Sample genotype (not yours): G/C
Altered Drug Response and Typical Cancer Risk
One copy of the variant allele slightly alters enzyme kinetics, leading to mixed effects on chemotherapy side effects and pain relief.
What this genotype means: Lower risk of chemotherapy-induced neuropathy; Slightly reduced response to codeine and tramadol; Typical prostate cancer risk.
Gene function and biological role
Gene Function: The CYP1B1 gene encodes cytochrome P450 1B1, a key enzyme involved in the metabolism of estrogens and various foreign compounds [1]. It plays a critical role in the hydroxylation of 17beta-estradiol into catechol estrogens, which are highly active hormone metabolites [2]. This enzymatic pathway is heavily studied due to its potential influence on hormone-sensitive tissues and chemical clearance [3]. Beyond hormone processing, this enzyme is also responsible for activating or breaking down several therapeutic drugs, including chemotherapy agents and pain medications [4].
Variant Impact: The rs1056836 variant, also known as Leu432Val or CYP1B1*3, is a missense mutation in exon 3 that alters the amino acid at position 432 from leucine to valine [5]. This specific change occurs near the heme-binding domain of the enzyme, altering its catalytic activity and substrate specificity [6]. The valine-encoding C allele is highly prevalent globally, appearing in nearly half of the population with significant variation across ancestries [7]. This alteration modifies how efficiently the enzyme processes both natural hormones like estrogen and synthetic drugs like chemotherapy agents [8].
Key Insight: This single genetic letter change simultaneously reduces the risk of prostate cancer while altering how the body processes common chemotherapy drugs and pain relievers.
Location: CYP1B1. Chromosome 2 · 2p22.2 · 38.1 Mb
Estimated prevalence by population
Global 29.3%; European 32.1%; African 5.1%; East Asian 78.7%; South Asian 63.9%; Americas 46.6%; Ashkenazi 23.4%; Finnish 41.0%; Middle Eastern 35.0%; Amish 41.3%.
Estimated GG genotype frequency.
Global 42.9%; European 49.1%; African 35.0%; East Asian 20.0%; South Asian 32.0%; Americas 43.3%; Ashkenazi 49.9%; Finnish 46.1%; Middle Eastern 48.3%; Amish 45.9%.
Estimated GC genotype frequency.
Global 27.9%; European 18.8%; African 59.9%; East Asian 1.3%; South Asian 4.0%; Americas 10.1%; Ashkenazi 26.6%; Finnish 13.0%; Middle Eastern 16.7%; Amish 12.8%.
Estimated CC genotype frequency.
Showing effects for G/G genotype
Cancer & Oncology
Prostate Cancer
Prostate Cancer. Evidence: 4/10. Source: PMID 22327650. Typical Risk.
Lung Cancer
Lung Cancer. Evidence: 4/10. Source: PMID 20395011. Typical Risk.
Pharmacogenomics
Chemotherapy Response
Chemotherapy Neuropathy. Evidence: 5/10. Source: PMID 24599932. Typical Risk.
Chemotherapy Nausea. Evidence: 5/10. Source: PMID 29507678. Typical Risk.
Pain Medication Response
Opioid Pain Response. Evidence: 5/10. Source: PMID 35102242. Typical Response.
Rare Genetic Disorders
Congenital Malformations
Congenital Glaucoma. Evidence: 9/10. Source: PMID 19597567. Typical Risk.
Showing effects for C/C genotype
Prostate Cancer. Evidence: 4/10. Source: PMID 22327650. ~70% Lower Risk.
Lung Cancer. Evidence: 4/10. Source: PMID 20395011. Slightly Higher Risk.
Chemotherapy Neuropathy. Evidence: 5/10. Source: PMID 24599932. Lower Risk.
Chemotherapy Nausea. Evidence: 5/10. Source: PMID 29507678. Increased Risk.
Opioid Pain Response. Evidence: 5/10. Source: PMID 35102242. Poorer Response.
Showing effects for G/C genotype
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Carrying two copies of the G allele results in the standard leucine amino acid at position 432 of the CYP1B1 enzyme. This configuration maintains baseline enzymatic activity for processing estrogens and clearing environmental toxins [1]. Clinical studies show a typical baseline risk for prostate cancer compared to those carrying the variant allele [2]. In the context of chemotherapy, this genotype is associated with standard rates of treatment-induced nausea and neuropathy [3]. Standard responses are also expected for common pain medications like codeine and tramadol [4]. Expert clinical panels have confirmed that this common genetic profile does not elevate the risk for congenital eye disorders [5].
Standard estrogen processing; Typical response to chemotherapy; Baseline prostate cancer risk.
Sample genotype: CC (Homozygous)
Carrying two copies of the C allele results in an enzyme entirely composed of the valine variant, which significantly alters hormone metabolism [1]. This metabolic shift is linked to a notable 70 percent reduction in prostate cancer risk in certain populations [2]. When undergoing chemotherapy, this genotype offers protection against nerve damage but increases the likelihood of experiencing treatment-induced nausea [3]. Additionally, the altered enzyme kinetics may result in a less effective response to opioid pain medications like codeine and tramadol [4]. While some data suggest a slight increase in lung cancer susceptibility, expert panels confirm this variant is completely benign regarding congenital glaucoma [5].
Significantly lower risk of prostate cancer; Reduced risk of chemotherapy-induced neuropathy; Higher risk of chemotherapy-induced nausea.
Sample genotype: GC (Heterozygous)
Possessing one copy of the C allele introduces the valine amino acid into half of the CYP1B1 enzymes, subtly changing how the body processes hormones and medications [1]. This intermediate status is associated with a lower likelihood of experiencing peripheral neuropathy when undergoing taxane-based chemotherapy [2]. However, it may also lead to a poorer response to certain opioid pain relievers like codeine and tramadol [3]. Some epidemiological studies suggest a minor increase in lung cancer susceptibility, particularly among smokers, though overall hormone-related cancer risks remain close to the population average [4]. Reassuringly, expert consensus confirms that this variant does not cause congenital glaucoma [5].
Lower risk of chemotherapy-induced neuropathy; Slightly reduced response to codeine and tramadol; Typical prostate cancer risk.
Variants with shared genetic architecture
rs1800440 · CYP1B1 Gene · Chr 2 · Skin Cancer Risk
rs10012 · CYP1B1 Gene · Chr 2 · Estrogen Metabolism
rs1056827 · CYP1B1 Gene · Chr 2 · Breast Cancer Risk
Association of variants in estrogen-related pathway genes with prostate cancer risk.
Association of the CYP1B1 Leu432Val polymorphism with the risk of prostate cancer: a meta-analysis.
Molecular analysis of CYP1B1 in Omani patients with primary congenital glaucoma: a pilot study.
The CYP1B1 Leu432Val polymorphism contributes to lung cancer risk: evidence from 6501 subjects.
Content updated August 2026.
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