Weightlifting itself does not increase hair loss, however if you are taking anabolic steroids such as testosterone and have a genetic predisposition for male pattern baldness (androgenic alopecia), then yes you could potentially speed up your hair loss if you are not taking a DHT blocker such as finasteride (Propecia).
If you are a body builder and take testosterone supplements this could increase the rate od hair loss. Otherwise, exercise should not contribute to hair loss.