What you carry at this position in your DNA and what research says about it.
Cellular Aging and Cancer Risk: 8/10 evidence, 60 publications.
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Sample genotype (not yours): C/C
Typical Telomere Maintenance and Lower Risk of Several Cancers
Standard telomerase activity supports typical cellular longevity and chromosome protection. This profile is associated with a lower risk of breast, ovarian, and brain cancers, though it carries a slightly higher baseline risk for prostate cancer.
What this genotype means: Typical telomere length maintenance; Lower risk of breast and brain cancers; Slightly higher risk of prostate cancer.
Sample genotype (not yours): C/T
Intermediate Telomerase Activity and Balanced Risk Profile
A single copy of the T allele leads to a slight reduction in telomerase activity. This results in an intermediate risk profile across several cancers and cardiovascular measurements.
What this genotype means: Slightly reduced telomerase activity; Typical baseline risk for most cancers; Typical blood pressure levels.
Sample genotype (not yours): T/T
Shorter Telomeres with Mixed Cancer and Cardiovascular Risks
Reduced telomerase activity can accelerate telomere shortening over time. This profile is linked to higher risks for breast, ovarian, and brain cancers, but offers protection against prostate cancer.
What this genotype means: Accelerated telomere shortening; Higher risk of breast, ovarian, and brain cancers; Lower risk of prostate cancer and pulmonary fibrosis.
Gene function and biological role
Gene Function: The TERT gene provides instructions for making telomerase reverse transcriptase, the essential catalytic subunit of the telomerase enzyme [1]. Telomerase plays a critical role in maintaining the protective caps at the ends of chromosomes, known as telomeres, which naturally shorten as cells divide [1]. In most mature body cells, telomerase is turned off, leading to progressive telomere shortening and eventual cellular aging [2]. However, in highly proliferative cells and the vast majority of cancer cells, telomerase is reactivated to grant cells indefinite replicative potential [2]. Consequently, genetic variations that alter TERT expression can influence both the rate of cellular aging and the susceptibility to various cancers [1] [2].
Variant Impact: The rs10069690 variant is located within intron 4 of the TERT gene and alters how the gene's genetic instructions are spliced [1]. Carrying the T allele creates an alternative splicing site that leads to the retention of intron 4, producing a truncated, non-functional telomerase protein [1]. This alternative splicing reduces the overall level of functional telomerase, which can accelerate telomere shortening over time [1] [2]. Because telomerase activity is a double-edged sword, this reduction in cellular lifespan lowers the risk of some cancers by limiting uncontrolled cell division, but increases the risk of others by promoting genomic instability [1] [2].
Key Insight: The same genetic variant that accelerates cellular aging and increases the risk of breast and brain cancers actually helps protect against prostate cancer and lung fibrosis by limiting the replicative potential of abnormal cells.
Location: TERT. Chromosome 5 · 5p15.33 · 1.3 Mb
Estimated prevalence by population
Global 44.6%; European 54.9%; African 16.8%; East Asian 67.5%; South Asian 55.4%; Americas 58.8%; Ashkenazi 45.9%; Finnish 49.6%; Middle Eastern 44.9%; Amish 52.2%.
Estimated CC genotype frequency.
Global 40.9%; European 38.4%; African 48.4%; East Asian 29.3%; South Asian 38.1%; Americas 35.8%; Ashkenazi 43.7%; Finnish 41.7%; Middle Eastern 44.2%; Amish 40.1%.
Estimated CT genotype frequency.
Global 14.4%; European 6.7%; African 34.8%; East Asian 3.2%; South Asian 6.6%; Americas 5.4%; Ashkenazi 10.4%; Finnish 8.7%; Middle Eastern 10.9%; Amish 7.7%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Cancer & Oncology
Breast Cancer
Breast Cancer. Evidence: 8/10. Source: PMID 23535731. Typical Risk.
Brain & Nervous System Cancers
Brain Cancer. Evidence: 8/10. Source: PMID 26424050. Typical Risk.
Gynecological Cancers
Ovarian Cancer. Evidence: 8/10. Source: PMID 23535731. Typical Risk.
Prostate Cancer
Prostate Cancer. Evidence: 8/10. Source: PMID 23535824. Slightly Increased.
Endocrine & Reproductive
Female Reproductive Health & Fertility
Uterine Fibroids. Evidence: 8/10. Source: PMID 30194396. Typical Risk.
Organ Systems
Respiratory Health
Pulmonary Fibrosis. Evidence: 8/10. Source: PMID 34594039. Slightly Increased.
Cardiovascular & Metabolic
Hypertension
Blood Pressure. Evidence: 8/10. Source: PMID 30224653. Typical Levels.
Showing effects for C/T genotype
Breast Cancer. Evidence: 8/10. Source: PMID 23535731. Slightly Increased.
Brain Cancer. Evidence: 8/10. Source: PMID 26424050. Slightly Increased.
Ovarian Cancer. Evidence: 8/10. Source: PMID 23535731. Slightly Increased.
Prostate Cancer. Evidence: 8/10. Source: PMID 23535824. Typical Risk.
Uterine Fibroids. Evidence: 8/10. Source: PMID 30194396. Slightly Increased.
Pulmonary Fibrosis. Evidence: 8/10. Source: PMID 34594039. Typical Risk.
Showing effects for T/T genotype
Breast Cancer. Evidence: 8/10. Source: PMID 23535731. ~1.1x Increased Risk.
Brain Cancer. Evidence: 8/10. Source: PMID 26424050. ~1.5x Increased Risk.
Ovarian Cancer. Evidence: 8/10. Source: PMID 23535731. ~1.14x Increased Risk.
Prostate Cancer. Evidence: 8/10. Source: PMID 23535824. Lower Risk.
Uterine Fibroids. Evidence: 8/10. Source: PMID 30194396. ~1.12x Increased Risk.
Pulmonary Fibrosis. Evidence: 8/10. Source: PMID 34594039. Lower Risk.
Blood Pressure. Evidence: 8/10. Source: PMID 30224653. Slightly Higher.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Standard telomerase function is maintained, allowing cells to rebuild the protective caps on chromosomes at a typical rate [1]. This normal cellular maintenance supports healthy tissue regeneration and standard cellular aging processes [1]. Large-scale genetic studies show that this typical activity is associated with a lower risk of developing breast cancer, ovarian cancer, and uterine fibroids [1] [2]. Brain tumors, such as gliomas and glioblastomas, are also less common with this genetic profile [3]. However, because highly active telomerase can occasionally allow abnormal cells to replicate indefinitely, there is a slightly higher risk of prostate cancer and pulmonary fibrosis compared to those with the T variant [4] [5]. Maintaining a healthy lifestyle with regular exercise and a balanced diet can further support natural cellular health and longevity.
Typical telomere length maintenance; Lower risk of breast and brain cancers; Slightly higher risk of prostate cancer.
Sample genotype: CT (Heterozygous)
A balanced cellular environment is created by carrying one copy of each allele, resulting in intermediate telomerase activity [1]. Some telomerase enzymes are produced in a truncated form, which slightly reduces the efficiency of chromosome end maintenance [1] [2]. This minor reduction in telomere maintenance capacity places risks for breast, ovarian, and brain cancers at a near-average level [1] [3]. Similarly, the risks for prostate cancer and pulmonary fibrosis remain close to the general population baseline [4] [5]. Blood pressure levels are also typical, with no major genetic push in either direction [6]. Focusing on cardiovascular health and routine cancer screenings is the most effective way to manage this balanced genetic profile.
Slightly reduced telomerase activity; Typical baseline risk for most cancers; Typical blood pressure levels.
Sample genotype: TT (Homozygous)
Reduced telomerase activity is common due to alternative splicing that produces a non-functional, truncated enzyme [1] [2]. This reduction in functional telomerase can lead to faster telomere shortening, potentially accelerating cellular aging [1]. Multiple genome-wide association studies link this profile to an increased risk of breast cancer, particularly estrogen-receptor-negative subtypes, as well as ovarian cancer [1] [3]. There is also a moderately higher risk of developing brain tumors, such as gliomas and glioblastomas [4]. Additionally, a small increase in systolic and diastolic blood pressure has been observed [5]. Conversely, the limited replicative potential of these cells provides a protective effect, lowering the risk of prostate cancer and pulmonary fibrosis [6] [7]. Engaging in stress-reducing activities, regular cardiovascular exercise, and staying up to date on recommended health screenings are highly beneficial.
Accelerated telomere shortening; Higher risk of breast, ovarian, and brain cancers; Lower risk of prostate cancer and pulmonary fibrosis.
Variants with shared genetic architecture
rs2242652 · TERT Gene · Chr 5 · Cancer Risk Trade-offs
rs2735940 · TERT Gene · Chr 5 · Colorectal Cancer Risk
rs2853677 · TERT Gene · Chr 5 · Cancer Susceptibility
Association analysis identifies 65 new breast cancer risk loci.
A cross-population atlas of genetic associations for 220 human phenotypes.
Identification of ten variants associated with risk of estrogen-receptor-negative breast cancer.
Content updated August 2026.
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