What this means

Male-pattern hair loss is highly heritable but very polygenic. The strongest known signal is on the X chromosome at the androgen receptor locus, but a second well-replicated autosomal signal sits at 20p11, where rs6113491 and neighbouring SNPs flag a roughly 1.6× increase in early-onset hair loss per risk allele. Combined with X-linked variants it builds toward a stronger predictive score, but individual SNPs only shift the odds modestly.

Male-pattern hair loss runs in families, but no single gene calls the shot — hundreds of small ones add up. The strongest signal sits on the X chromosome, but this spot on chromosome 20 is the next best-known. Each copy of the "risk" version bumps the odds of early hair loss by about 1.6 times, but the bump only really shows when it stacks with other genes. Hormones and age still drive most of what happens.

Caveats

• Hair loss is dominated by hormones (DHT) and age, not by any single SNP.
• The strongest single locus is on the X chromosome at the androgen receptor — this is an autosomal modifier.
• Effect sizes for single SNPs are modest; useful predictions need polygenic scores.
• Hair loss patterns in women are less well-characterised by this locus.

References

• Hillmer et al. — Susceptibility variants for male-pattern baldness on chromosome 20p11 (Nature Genetics, 2008)
• Heilmann-Heimbach et al. — Meta-analysis identifies novel risk loci and yields systematic insights into the biology of male-pattern baldness (Nature Communications, 2017)