I started lifting 2 years ago. That's also when I started to see my hair thinning. My gut feeling tells me it's related. Even got back pimples since then.
My hair loss became noticeable at 25, the year I began lifting weights. I don't like stating something without proof, but there are many people here who started experiencing hair loss right around the time they started weight lifting. I don't think it's a coincidence.