That's not true. And it isn't normal for an 18 year old to be experiencing hairloss.
If it happens: it's normal. Simple as that.
20 % of men already start losing hair in their late teens and most of the time it's the genetics fault.
You can take medication though.
His hairline is not receding What are you people talking about? Some guys just have a hairline like that, and it's ok. Stay at home watching boys on tumblr and ignore the regular guys IRL, I guess