What you carry at this position in your DNA and what research says about it.
Endometrial Cancer Risk: 6/10 evidence, 13 publications.
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Sample genotype (not yours): C/C
Lower Risk of Endometrial Cancer
Lower aromatase enzyme activity results in reduced circulating estrogen levels. This profile is associated with a lower risk of developing hormone-driven endometrial cancer.
What this genotype means: Lower circulating estrogen levels; Reduced risk of endometrial cancer; Slightly higher testosterone levels.
Sample genotype (not yours): A/A
Increased Risk of Endometrial Cancer
Highly efficient aromatase activity leads to higher circulating estrogen levels. This profile increases endometrial cancer risk but is linked to better outcomes during breast cancer therapy.
What this genotype means: Higher circulating estrogen levels; Increased risk of endometrial cancer; Better survival outcomes on anastrozole therapy.
Sample genotype (not yours): C/A
Slightly Increased Risk of Endometrial Cancer
Moderate aromatase activity leads to typical to slightly elevated estrogen levels. This intermediate profile is linked to a modest increase in endometrial cancer risk.
What this genotype means: Typical to slightly higher estrogen levels; Modestly increased risk of endometrial cancer; Typical hormone balance.
Gene function and biological role
Gene Function: The CYP19A1 gene encodes aromatase, the key enzyme responsible for converting androgens into estrogens like estrone and estradiol [1]. This conversion is the primary source of estrogen in postmenopausal women and plays a critical role in maintaining bone density, lipid profiles, and reproductive tissue health [1]. Because aromatase regulates the balance of sex hormones, variations in this gene can significantly alter lifetime exposure to estrogen [2]. Consequently, CYP19A1 activity is closely linked to hormone-sensitive conditions, including certain cancers and cardiovascular health [2].
Variant Impact: The rs727479 variant is an intronic change within the CYP19A1 gene that acts as a major genetic determinant of circulating estrogen levels [1]. The A allele is associated with increased expression of the aromatase enzyme, leading to higher circulating levels of estrone and estradiol [1]. This elevated estrogen exposure is a known driver of endometrial cell proliferation, which increases the risk of endometrial cancer [2]. Conversely, the C allele is linked to lower aromatase activity, resulting in lower estrogen but higher testosterone levels [3].
Key Insight: The same genetic variant that increases estrogen levels and raises endometrial cancer risk also predicts a better survival response to the breast cancer drug anastrozole.
Location: CYP19A1. Chromosome 15 · 15q21.2 · 51.2 Mb
Estimated prevalence by population
Global 10.1%; European 12.4%; African 4.7%; East Asian 9.8%; South Asian 6.5%; Americas 14.3%; Ashkenazi 10.5%; Finnish 11.6%; Middle Eastern 19.2%; Amish 15.0%.
Estimated CC genotype frequency.
Global 42.1%; European 45.6%; African 33.9%; East Asian 43.0%; South Asian 38.0%; Americas 47.0%; Ashkenazi 43.8%; Finnish 45.0%; Middle Eastern 49.2%; Amish 47.5%.
Estimated CA genotype frequency.
Global 47.7%; European 41.9%; African 61.4%; East Asian 47.2%; South Asian 55.5%; Americas 38.7%; Ashkenazi 45.8%; Finnish 43.4%; Middle Eastern 31.5%; Amish 37.5%.
Estimated AA genotype frequency.
Showing effects for C/C genotype
Cancer & Oncology
Gynecological Cancers
Endometrial Cancer. Evidence: 3/10. Source: PMID 26574572. Lower Risk.
Endocrine & Reproductive
Hormone Levels & Endocrine Regulation
Estrogen Levels. Evidence: 6/10. Source: PMID 29325096. Lower Estrogen.
Testosterone Levels. Evidence: 4/10. Source: PMID 34822396. Higher Testosterone.
Pharmacogenomics
Chemotherapy Response
Anastrozole Response. Evidence: 5/10. Source: PMID 27747906. Typical Response.
Showing effects for A/A genotype
Endometrial Cancer. Evidence: 3/10. Source: PMID 26574572. Increased Risk.
Estrogen Levels. Evidence: 6/10. Source: PMID 29325096. Higher Estrogen.
Testosterone Levels. Evidence: 4/10. Source: PMID 34822396. Lower Testosterone.
Anastrozole Response. Evidence: 5/10. Source: PMID 27747906. Better Survival.
Showing effects for C/A genotype
Endometrial Cancer. Evidence: 3/10. Source: PMID 26574572. Slightly Higher Risk.
Estrogen Levels. Evidence: 6/10. Source: PMID 29325096. Typical Estrogen.
Testosterone Levels. Evidence: 4/10. Source: PMID 34822396. Typical Levels.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Aromatase enzyme activity is lower with this genetic profile, resulting in reduced circulating estrogen levels [1]. Postmenopausal women with this combination have a lower risk of developing endometrial cancer compared to those carrying the A allele [2]. Men with this profile may have slightly higher testosterone levels due to reduced conversion of androgens into estrogens [3]. Additionally, this genotype is linked to a slightly higher waist-to-hip ratio, reflecting differences in hormone-driven fat distribution [4]. While lower estrogen is protective against certain cancers, it can sometimes influence bone density over time [1].
Lower circulating estrogen levels; Reduced risk of endometrial cancer; Slightly higher testosterone levels.
Sample genotype: AA (Homozygous)
Aromatase enzyme activity is highly efficient, leading to higher circulating levels of estrone and estradiol [1]. This elevated lifetime exposure to estrogen is linked to an increased risk of endometrial cancer, particularly after menopause [2]. Conversely, postmenopausal breast cancer patients with this profile show improved survival outcomes when treated with the aromatase inhibitor anastrozole [3]. This genotype is also associated with lower circulating testosterone levels due to more rapid conversion into estrogen [4]. Additionally, a lower waist-to-hip ratio is commonly observed with this profile, reflecting estrogen-driven fat distribution [5].
Higher circulating estrogen levels; Increased risk of endometrial cancer; Better survival outcomes on anastrozole therapy.
Sample genotype: CA (Heterozygous)
Aromatase enzyme activity is moderate, leading to typical to slightly elevated estrogen levels in the body [1]. Having one copy of the A allele is associated with a modest, dose-dependent increase in the risk of endometrial cancer in postmenopausal women [2]. This intermediate profile generally results in typical hormone balance and average body fat distribution [3]. Because estrogen levels remain in the typical range, the overall impact on bone density and cardiovascular health is balanced [1]. However, lifestyle factors like body mass index can interact with this genotype to further influence hormone levels [2].
Typical to slightly higher estrogen levels; Modestly increased risk of endometrial cancer; Typical hormone balance.
Variants with shared genetic architecture
rs4646 · CYP19A1 Gene · Chr 15 · Estrogen and Hair Health
rs700519 · CYP19A1 Gene · Chr 15 · Hormone Balance
rs2899472 · CYP19A1 Gene · Chr 15 · Estrogen and Bone Density
CYP19A1 fine-mapping and Mendelian randomization: estradiol is causal for endometrial cancer.
Sex-Specific Causal Relations between Steroid Hormones and Obesity-A Mendelian Randomization Study.
Content updated August 2026.
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