Baldness isn't inherited only from the mother's side. However, one of the most studied genes associated with hair loss, AR (the androgen receptor gene), is inherited through the mother. This gene is located on the X chromosome, and men inherit their X chromosome from their mother. That's why men inherit the variants of the AR gene that affect hair follicle sensitivity to androgens specifically from their mother.
BUT male pattern baldness is a polygenic condition, meaning that the predisposition to it is determined by many different genes inherited from both the mother and the father. Many other genetic variants associated with baldness are located on regular, non-sex chromosomes (autosomes). Men inherit these from both parents. That's why having a bald father is also a significant risk factor.
In a large 2018 study involving more than 205,000 men, researchers identified hundreds of genetic regions associated with male pattern baldness. A significant proportion of these are located on autosomes, which are inherited from both parents.
So:
- If your maternal grandfather is bald, your risk may be higher.
- If your father is bald, your risk may also be higher.
- If both have thick hair, that doesn't guarantee their son won't experience hair loss.
- If both are bald, that still doesn't mean their son will inevitably go bald.