What you carry at this position in your DNA and what research says about it.
Thyroid Cancer Risk: 10/10 evidence, 35 publications.
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Sample genotype (not yours): A/A
Significantly Higher Thyroid Cancer Risk
An A/A genotype is linked to a 3.1-fold increase in thyroid cancer risk. However, this genetic profile also correlates with a lower risk of hypothyroidism.
What this genotype means: Significantly higher risk of differentiated thyroid cancer; Lower risk of developing hypothyroidism; Lower risk of developing goiter.
Sample genotype (not yours): A/G
Moderately Higher Thyroid Cancer Risk
An A/G genotype is associated with a 1.77-fold increase in thyroid cancer risk, with typical risks for other thyroid conditions.
What this genotype means: Moderately higher risk of differentiated thyroid cancer; Typical risk of hypothyroidism; Typical risk of goiter.
Sample genotype (not yours): G/G
Typical Thyroid Cancer Risk
A G/G genotype is associated with a typical risk of thyroid cancer, though it carries a slightly higher risk of hypothyroidism.
What this genotype means: Typical risk of differentiated thyroid cancer; Higher risk of developing hypothyroidism; Higher risk of developing goiter.
Gene function and biological role
Gene Function: The PTCSC2 gene, or papillary thyroid carcinoma susceptibility candidate 2, is a long non-coding RNA gene located on chromosome 9. It is highly expressed in normal thyroid tissue but frequently down-regulated in thyroid tumors [1]. PTCSC2 acts as a tumor suppressor and plays a key role in maintaining normal thyroid cell function [1]. This locus is situated in close proximity to the FOXE1 gene, which is crucial for thyroid gland development and hormone regulation [2]. Genetic variations in this region can disrupt the coordinated expression of both PTCSC2 and FOXE1, predisposing individuals to thyroid disorders [2].
Variant Impact: The rs965513 variant is an intronic single nucleotide polymorphism located within the PTCSC2 gene locus. This genetic change acts as a long-range enhancer modulator, affecting the transcriptional activity of both PTCSC2 and the neighboring FOXE1 gene [3]. The risk-associated A allele is linked to significantly reduced expression of these protective genes in healthy thyroid tissue [4]. Such a reduction in gene expression is thought to impair normal thyroid cell differentiation, making cells more susceptible to malignant transformation [4]. It represents one of the strongest genetic risk factors identified for sporadic and radiation-induced thyroid cancer [5].
Key Insight: The same genetic variant that increases the risk of thyroid cancer actually decreases the risk of developing an underactive thyroid (hypothyroidism).
Location: PTCSC2. Chromosome 9 · 9q22.33 · 97.8 Mb
Estimated prevalence by population
Global 8.2%; European 11.5%; African 2.6%; East Asian 1.2%; South Asian 5.2%; Americas 8.3%; Ashkenazi 10.4%; Finnish 11.0%; Middle Eastern 8.1%; Amish 27.0%.
Estimated AA genotype frequency.
Global 38.3%; European 44.8%; African 27.1%; East Asian 19.2%; South Asian 35.2%; Americas 41.0%; Ashkenazi 43.7%; Finnish 44.4%; Middle Eastern 40.7%; Amish 49.9%.
Estimated AG genotype frequency.
Global 53.5%; European 43.7%; African 70.3%; East Asian 79.6%; South Asian 59.6%; Americas 50.8%; Ashkenazi 45.9%; Finnish 44.6%; Middle Eastern 51.2%; Amish 23.0%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Cancer & Oncology
Thyroid & Endocrine Cancers
Thyroid Cancer. Evidence: 10/10. Source: PMID 19198613. ~3.1x Increased Risk.
Endocrine & Reproductive
Hormone Levels & Endocrine Regulation
Hypothyroidism. Evidence: 8/10. Source: PMID 22493691. Lower Risk.
Nontoxic Goiter. Evidence: 8/10. Source: PMID 39024449. Lower Risk.
Showing effects for A/G genotype
Thyroid Cancer. Evidence: 10/10. Source: PMID 19198613. ~1.77x Increased Risk.
Hypothyroidism. Evidence: 8/10. Source: PMID 22493691. Typical Risk.
Nontoxic Goiter. Evidence: 8/10. Source: PMID 39024449. Typical Risk.
Showing effects for G/G genotype
Thyroid Cancer. Evidence: 10/10. Source: PMID 19198613. Typical Risk.
Hypothyroidism. Evidence: 8/10. Source: PMID 22493691. Increased Risk.
Nontoxic Goiter. Evidence: 8/10. Source: PMID 39024449. Increased Risk.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Research indicates that the A/A genotype is associated with a 3.1-fold increased risk of developing differentiated thyroid cancer compared to non-carriers [1]. This variant resides near the FOXE1 gene, which is essential for thyroid development and hormone synthesis [2]. The A allele reduces the expression of protective genes in healthy thyroid tissue, potentially facilitating tumor development [3]. Interestingly, this genetic profile is also associated with a lower risk of developing hypothyroidism and goiter [4]. While the relative risk of thyroid cancer is significantly higher, the absolute lifetime risk remains low for most individuals. Regular physical exams and neck ultrasounds can assist in early detection and monitoring if recommended by a physician. Maintaining a healthy lifestyle and avoiding unnecessary radiation exposure are also beneficial.
Significantly higher risk of differentiated thyroid cancer; Lower risk of developing hypothyroidism; Lower risk of developing goiter.
Sample genotype: AG (Heterozygous)
Studies show that the A/G genotype is associated with a moderately elevated risk of differentiated thyroid cancer, showing a 1.77-fold increase compared to those with the G/G genotype [1]. This effect is driven by the A allele, which alters the regulation of the nearby FOXE1 gene, a key player in thyroid cell differentiation [2]. The single A allele moderately decreases the expression of thyroid-protective transcripts [3]. For other thyroid conditions like hypothyroidism and goiter, this heterozygous genotype generally confers a typical, average risk [4]. Because thyroid cancer is relatively rare, a moderate increase in relative risk still translates to a low absolute risk. Standard wellness checkups that include thyroid palpation are usually sufficient for routine monitoring. Awareness of family history and limiting radiation exposure are practical ways to manage overall thyroid health.
Moderately higher risk of differentiated thyroid cancer; Typical risk of hypothyroidism; Typical risk of goiter.
Sample genotype: GG (Homozygous)
The G/G genotype is associated with a baseline, typical risk of developing differentiated thyroid cancer [1]. This genotype is considered the normal or protective state for thyroid oncogenesis because it maintains higher expression levels of the FOXE1 and PTCSC2 genes [2]. However, the G allele is also the risk allele for certain benign thyroid conditions [3]. Individuals with the G/G genotype have a higher susceptibility to developing hypothyroidism and goiter compared to carriers of the A allele [3] [4]. Fortunately, hypothyroidism is a highly manageable condition that is easily detected through standard blood tests like thyroid-stimulating hormone levels. Maintaining adequate dietary iodine intake is important for supporting overall thyroid function. Regular medical checkups can help monitor thyroid hormone levels and address any symptoms of an underactive thyroid.
Typical risk of differentiated thyroid cancer; Higher risk of developing hypothyroidism; Higher risk of developing goiter.
Variants with shared genetic architecture
rs121912648 · TG Gene · Chr 8 · Thyroid Hormone Health
rs151234 · APOBR Gene · Chr 16 · Type 1 Diabetes Risk
rs16857609 · DIRC3 Gene · Chr 2 · Cancer Risk
Discovery of common variants associated with low TSH levels and thyroid cancer risk.
The FOXE1 locus is a major genetic determinant for radiation-related thyroid carcinoma in Chernobyl.
Common variants on 9q22.33 and 14q13.3 predispose to thyroid cancer in European populations.
Novel associations for hypothyroidism include known autoimmune risk loci.
Diversity and scale: Genetic architecture of 2068 traits in the VA Million Veteran Program.
Content updated August 2026.
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