One of the more genetic common cancers, and two studies from the same group both point the same way: the loci that raise risk also lower thyroid-stimulating hormone, and the strongest one sits on the gene that builds the thyroid gland in the embryo.
The thyroid is a small gland at the base of the neck that makes hormones — thyroxine (T4) and triiodothyronine (T3) — that set the pace of metabolism throughout the body. It is controlled by thyroid-stimulating hormone (TSH) from the pituitary gland, in a feedback loop: more thyroid hormone, less TSH, and back again.
Thyroid cancer is, among common cancers, unusually genetic — twin and family studies put its heritability among the highest of any cancer studied this way — which is what made it a productive target for genome-wide scanning early.
Both papers behind this page came from the same Icelandic group. The first, in 2009, scanned thyroid cancer directly: 192 Icelandic cases against 37,196 controls, with replication in further European populations. It found two loci — one on 9q22.33, near FOXE1, with an odds ratio of 1.75; and one on 14q13.3, near NKX2-1, with an odds ratio of 1.37. Both risk alleles were also associated with lower TSH in the general population.
The second paper, in 2012, came at the same territory from the other direction. Rather than scanning cancer, it scanned TSH levels in 27,758 Icelanders, then tested the loci that moved TSH against thyroid cancer case-control data. Three were confirmed, and one of them was in the same 14q13.3 region the 2009 paper had already found — a second, uncorrelated variant there, with an odds ratio of 2.09, the largest effect on this page. A second locus, on 8p12, sits near NRG1 — neuregulin 1, a signalling protein — and showed a very strong association with NRG1's own expression level in blood.
Two independent designs, five years apart, converging on the same region and the same relationship to TSH is the kind of agreement genetics does not produce by chance. NKX2-1 (also called TTF1) is a transcription factor required for the thyroid gland to form during embryonic development, and it stays active in thyroid follicular cells — the hormone-producing cells — for life. A locus near the gene that builds the thyroid follicular cell, shifting both the hormone that drives that cell and the cell's own cancer risk, is a coherent biological story rather than a coincidental one.
This site's strongest single locus from the 2009 paper — 9q22.33, near FOXE1, odds ratio 1.75 — is not on this page. The collector recorded a different marker in the neighbouring 14q13.3 region instead. The page says so rather than implying the strongest finding is represented here.
All three variants here shift risk by a fraction, in a population that already has a wide range of thyroid cancer risk from other causes — the most established of which is radiation exposure, especially in childhood. None of them diagnoses the disease or predicts an individual case.
What actually gets thyroid cancer found. A lump or swelling in the neck, often noticed by the person themselves or found on an examination for something else, is what leads to an ultrasound and, if needed, a fine-needle biopsy. Most thyroid nodules are not cancer. Nothing on this page detects the disease and nothing here should delay that evaluation.
Both risk loci associate with lower TSH in the general population — which, given the feedback loop between the pituitary and the thyroid, points toward a thyroid gland working slightly differently from the start, rather than TSH itself being the cause. This is a mechanistic clue for researchers, not a screening signal: a normal TSH blood test does not rule out thyroid cancer, and TSH testing is not used to assess this genetic risk.
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Thyroid Cancer comes down to these specific, well-studied positions — not a diagnosis.
Databases, guidelines and references
No. The variants here each shift risk by a fraction and none of them detects the disease. A lump or nodule found on examination, followed by ultrasound and often a biopsy, is what actually finds thyroid cancer.
No. The genetic loci here associate with lower average TSH across a population, which is a research clue about mechanism, not something used to assess an individual's cancer risk. TSH testing and thyroid cancer risk are not the same thing.
Because two different starting points — scanning cancer directly, and separately scanning TSH levels — converged on 14q13.3, near NKX2-1, a gene required to build the thyroid gland in the embryo and active in thyroid cells for life. Agreement like that across independent designs is what makes a genetic finding believable.
Radiation exposure, especially in childhood, is a far larger and better-established risk factor for thyroid cancer than anything on this page. If that applies to you, the useful step is discussing surveillance with a doctor, not a genotype.
Free to reuse. This page's text is original writing from freely-available research, licensed CC BY 4.0 — reuse it, including commercially, with attribution to MyGeneLog. It's general research-derived information, not medical advice or a diagnosis — see Terms of Use.