Q: Why do some people have a full head of hair into their seventies or eighties and others start to go bald in their late teens or early twenties? — E.Z., Darien, CT

A: The difference is genetic with the inheritance coming from either side of the family.

Although a person will have the genes his/her whole life, a gene’s expression (also called phenotype) can be quite variable. The factors that cause this variability are still unknown.

Read more about the Genetics of Hair Loss