The idea that hair loss is determined primarily by the mother’s side of the family — specifically the maternal grandfather — is one of the most persistent myths in hair loss genetics. The truth is more complex and, for patients trying to predict their own trajectory, more nuanced.
Androgenetic alopecia is a polygenic condition — controlled by variants across multiple genes rather than a single gene. This means that both maternal and paternal inheritance contribute to the susceptibility. Your father’s hair pattern is just as relevant as your maternal grandfather’s when assessing your own risk.
The androgen receptor gene (AR) is located on the X chromosome, which men inherit from their mothers. Variants in this gene that increase the sensitivity of androgen receptors in hair follicles have a particularly strong association with male pattern baldness — which is why the maternal grandfather association has some validity. But AR variants explain only a fraction of the genetic component of androgenetic alopecia.
Research published in large genome-wide association studies has identified more than 350 genetic loci associated with male hair loss, spanning many chromosomes and both maternal and paternal lines. The combined predictive power of these loci is still imperfect — genetic testing for hair loss risk exists but cannot yet predict individual outcomes reliably enough to inform clinical decisions.
The practical guidance: look at both sides of your family. Your father’s hair, your mother’s father’s hair, your paternal grandfather’s hair, and your uncles on both sides all provide relevant information. No single family member’s pattern definitively predicts yours.
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