Any possibility that weightlifting causes hairfall?i read that after weight lift testostrone converts in dht which cause hairloss. using minoxidil 10%

You have one: Theory. My theory would be stress from the activity and shifting of blood flow from scalp to muscles of extremities. Genetics would also play a role.

Doubt it: This is one of many "pop" notions about testosterone that circulates in gyms. Lifting ups testosterone only slightly. Your hair loss is primarily genetic; you can suppress it by suppressing your natural testosterone, but if you're a bodybuilder, you probably don't want to do that. Most people will be much more impressed with your lean muscle than with your taking measures to keep your hair.