How large the thyroid gland is varies between healthy people, and part of that is inherited. A 2011 study of 3,620 people found four loci for thyroid volume — and the same positions raised the odds of goiter.
Thyroid volume is simply the size of the thyroid gland, measured by ultrasound. It varies between healthy people, it grows when iodine is short, and an enlarged thyroid is what a goiter is. Studies of siblings had shown that genes account for a substantial part of the difference in thyroid size between people; which genes was not known.
Teumer et al. 2011 ran a genome-wide study of thyroid volume in 3,620 participants of the Study of Health in Pomerania, in north-east Germany, and found four loci at genome-wide significance. All four were replicated in an independent sample of 1,290 participants of the KORA study. This page holds 5 variants from those loci.
Two of the four loci are independent signals at one gene, CAPZB — one upstream of it and one inside it. CAPZB encodes part of a protein that caps the growing end of actin filaments, and actin remodelling is what a thyroid cell uses to engulf stored colloid when it needs to release thyroid hormone. The third locus marks FGF7, a growth factor from a family discussed as signals in thyroid development. The fourth sits in a stretch of chromosome 16 with no known genes, a "gene desert" at 16q23 — next to a predicted gene that had been removed from the database as an artefact, and which the authors then showed by experiment to be real.
The same positions were associated with goiter itself: in the catalogue's records of this study, rs10917468 carried an odds ratio of 1.52 for goiter, rs4338740 1.45 and rs12045440 1.38. That is the point of studying a measurement: the variants that make a thyroid slightly larger in a healthy person are the ones that make an enlarged thyroid more likely. This site's benign nodular goiter page holds the much larger 2026 study of the disease, and TSH levels the hormone that tells the thyroid to grow.
Thyroid size is measured by ultrasound, not estimated from a genotype. None of the 5 variants on this page is used by any guideline to diagnose a goiter or to decide whether a thyroid needs further testing.
An enlarged thyroid is assessed with ultrasound and thyroid function tests, and iodine intake is the first thing a clinician considers. The variants here describe why thyroid size differs between people in a population.
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Thyroid Volume comes down to these specific, well-studied positions — not a diagnosis.
The studies behind these variants recruited participants from different ancestries — a result found in one population doesn't always transfer to another. Based on 5 of 5 linked studies with a resolved discovery ancestry.
Databases, guidelines and references
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Thyroid Volume. MyGeneLog™. https://www.mygenelog.com/conditions/thyroid-volume
The size of the thyroid gland, measured by ultrasound. It varies between healthy people and grows when iodine is short; an enlarged thyroid is called a goiter.
Partly. Sibling studies show a substantial genetic contribution, and a 2011 genome-wide study of 3,620 people found four associated loci, replicated in 1,290 more.
Two of the four loci are at CAPZB, a gene involved in the actin remodelling thyroid cells use to release hormone. A third marks FGF7, a growth factor, and the fourth is in a gene desert on chromosome 16.
No. These are population-level associations. Thyroid size is measured by ultrasound, and no guideline uses a genotype to diagnose or predict a goiter.
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