Excessive hair growth in women is usually attributed to one cause — but a genome-wide study designed specifically to look beyond it found a rare, unusually strong-effect variant that most studies its size would have missed.
Hirsutism — excessive hair growth in women, typically in male-pattern areas such as the face, abdomen and chest — affects roughly 5-10% of women. Most commonly attributed to polycystic ovary syndrome (PCOS), its causes are actually heterogeneous, spanning genetic and ethnic background as well as several distinct endocrine conditions. This page holds 4 variants from a 2026 study built specifically to look past the PCOS explanation.
The study, titled plainly "Hirsutism beyond PCOS," combined 4,834 cases and 352,966 controls across multiple ancestries and found 7 associated loci, 4 of them newly reported. What sets it apart is a deliberate second step: analyzing the Finnish FinnGen cohort separately, specifically because Finland's population history (a genetic bottleneck) enriches for rare variants that carry unusually large effects — variants a study of ordinary size and composition would likely never catch.
That approach found rs199649605, a missense variant near FGF5 — a gene that regulates the hair follicle growth cycle — present in only about 0.5% of the general population but with a strikingly large effect (odds ratio 5.02, 95% CI 3.06-8.21). A variant this rare, with an effect size this large, is genuinely unusual among the findings on this site, most of which shift risk by a few percent per copy across common variants. This page's other three variants — rs150735020 and rs180731645, both in CFAP299, and rs544265360, near ANTXR2 — come from the same study's broader, cross-ancestry analysis.
The study's own stated finding on mechanism: hirsutism shares genetic architecture with PCOS itself and with metabolic traits including obesity and type 2 diabetes, and the evidence points to both androgen-dependent and androgen-independent biological routes to excessive hair growth — not PCOS as the sole explanation the condition's reputation suggests.
Hirsutism is diagnosed clinically, from the pattern of hair growth, alongside investigation for its underlying cause (most often PCOS, but not always) — not by genotype. None of the 4 variants on this page are used by any guideline to diagnose hirsutism or select treatment.
The loci described above come from a large, deliberately ancestry-diverse genetic study. Even the rare FGF5 variant with its unusually large effect size is a population-level finding from a study cohort, not an individual diagnostic test — the actual clinical workup for hirsutism still centers on identifying its underlying endocrine cause.
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Hirsutism comes down to these specific, well-studied positions — not a diagnosis.
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Hirsutism. MyGeneLog™. https://www.mygenelog.com/conditions/hirsutism
Excessive hair growth in women, typically in male-pattern areas such as the face, abdomen and chest, affecting roughly 5-10% of women.
No. Polycystic ovary syndrome is the most common cause, but a 2026 genetic study titled "Hirsutism beyond PCOS" found genetic contributors independent of it, with evidence for both androgen-dependent and androgen-independent mechanisms.
A rare missense variant near FGF5, found by specifically analyzing the Finnish FinnGen cohort for large-effect rare variants. Present in only about 0.5% of people, it carries an unusually large effect (odds ratio 5.02) compared to the small-effect common variants typical of most genetic findings.
No. Hirsutism is diagnosed clinically alongside investigation of its underlying cause. These are population-level genetic findings, not a way to predict an individual case.
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