Where your DNA places you among other people, and the studies behind it.
Not tailored to your result, and not medical advice
Avoid Unnecessary Neck Radiation: Ionizing radiation reaching the thyroid, particularly during childhood and adolescence, has long been considered the only established modifiable risk factor for thyroid cancer, with the clearest evidence coming from childhood radiotherapy and from nuclear fallout exposures such as Chernobyl. The same review notes that only a minority of people with differentiated thyroid cancer report any history of childhood radiation exposure, so this explains part of the picture rather than all of it, and most thyroid cancer is not traceable to an exposure a person chose. When a scan or treatment involving the head, neck or chest is being considered, asking the clinician what it is for and whether an alternative exists is a reasonable conversation to have. Nature Reviews Endocrinology (PMC)
Watch Long-Term Weight Gain: In a pooled analysis of 538,857 adults across 13 cohorts in the Asia Cohort Consortium, followed for a mean of 15.1 years and yielding 1,132 thyroid cancers, each 5 kg/m2 increase in body mass index was associated with a 25% higher rate in men (HR 1.25, 95% CI 1.01 to 1.55), while in women the association was weaker and not statistically significant (HR 1.07, 95% CI 0.97 to 1.18). Higher body weight has been associated with thyroid cancer across many cohort studies, though this is observational evidence and does not establish cause. The habits that keep weight steady are the ordinary ones, including diet quality, sleep, and the roughly 150 minutes of moderate activity a week that national physical-activity guidance describes. Thyroid (PMC)
Get Iodine From Everyday Food: The thyroid needs iodine to make its hormones, and a comprehensive review of animal and human studies concluded that the available evidence suggests iodine deficiency is a risk factor for thyroid cancer, particularly the follicular subtype, plausibly through chronic TSH stimulation of thyroid cells. This is also the item where the honest answer is that the evidence is thin. The same review pooled four case-control studies and found 23% lower odds of thyroid cancer in the highest quantile of iodine intake versus the lowest, a difference that was borderline and not statistically significant (OR 0.77, 95% CI 0.58 to 1.02), and it describes the role of iodine intake in thyroid cancer as still uncertain after decades of study. Ordinary dietary sources such as iodised salt, dairy, eggs, fish and seaweed cover normal requirements without the concentrated amounts found in kelp supplements. Thyroid Research (PMC)
Have a Neck Lump Checked: The usual presenting sign of thyroid cancer is a lump in the front lower part of the neck that feels hard, is not painful, and slowly gets bigger. NHS guidance describes seeing a GP about a new neck lump or an existing lump that is getting bigger, about a hoarse voice, sore throat or cough lasting more than three weeks, or about pain in the front of the neck or a feeling of something pressing against it, and getting urgent help for difficulty swallowing or breathing. That guidance is also explicit that these symptoms are very common and can be caused by many different conditions, so this is about getting a look rather than assuming the worst. NHS
Understand the Overdiagnosis Problem: Modelling suggests much of the recent rise in thyroid cancer reflects extra detection rather than extra disease. A simulation study of US adults covering 1991 to 2019 estimated that 72% to 94% of papillary thyroid cancer cases were overdiagnosed, meaning tumors found that would never have caused symptoms, amounting to between 443,212 and 573,705 women and between 107,804 and 154,504 men. The same modelling found that cutting thyroid ultrasound use for non-palpable nodules by 33% or 67% would have lowered recorded incidence in 2019 by 17% and 41%, with less than a 0.1% change in overall mortality. Whether to image a thyroid is a judgement that belongs with a clinician who knows your symptoms and history. JAMA Network Open (PMC)
How much of this is genetic?
Genetics explains 53% of why people differ in this trait. The rest is environment, daily habits and chance.
Heritability estimate: Analysis of the Swedish Family-Cancer Database estimated the heritable component of thyroid cancer liability at about 53%, the highest of the 15 common cancers examined (Czene et al., Int J Cancer 2002).
Background and further reading
Thyroid cancer is the most common cancer of the endocrine system. The great majority of cases are differentiated thyroid cancers, chiefly papillary thyroid carcinoma, which grow slowly and are usually very treatable. It often presents as a painless lump or nodule in the neck, though many cases are now found incidentally on imaging done for other reasons. Thyroid cancer is roughly three times more common in women than in men, and incidence rose sharply in many countries over recent decades, a trend attributed largely to increased detection of small tumors that would never have caused harm. Overall survival for differentiated thyroid cancer is excellent, with long-term survival above 95% for localized disease.
Genetic Basis: Thyroid cancer has one of the strongest inherited components of any common cancer. Studies of families and twins estimate that a large share of the variation in liability is heritable, and having a first-degree relative with thyroid cancer is associated with one of the highest familial relative risks reported across cancers. Most of this is polygenic, reflecting the combined effect of many common variants rather than a single mutation. Genome-wide association studies have identified consistent signals near FOXE1 (also called TTF2, on chromosome 9q22) and NKX2-1 (also called TITF1, on 14q13), both master transcription factors for thyroid development, as well as loci such as DIRC3 and MBIP. Rare high-penetrance syndromes are separate from this polygenic score: germline RET mutations cause hereditary medullary thyroid cancer (MEN2), and conditions such as familial adenomatous polyposis, Cowden syndrome, and DICER1 syndrome raise risk of specific thyroid tumor types.
Contributing Factors: The best-established environmental cause is exposure to ionizing radiation, particularly during childhood, whether from medical treatment or nuclear fallout. Other associated factors include iodine intake at the extremes (both deficiency and excess), a personal history of benign thyroid disease such as goiter or nodules, and higher body weight. Female sex and, for detection, access to neck imaging and ultrasound also strongly influence how often thyroid cancer is diagnosed. Because a polygenic score reflects only common inherited variants, it captures just part of overall predisposition and does not account for radiation history, family history of rare syndromes, or these other influences.
The published research behind your score, and the variants it draws on.
4 published scores from 3 studies
The thyroid cancer score combines 4 polygenic scores drawn from 3 published studies.
These traits are influenced by some of the same genes and variants as this one
Content updated August 2026.
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