Sex and watching ���� increase testesterone,stretching the penis increases to.
I was on antidepressive pill which decrease testesterone,after the pills i know when my testesteron is increased,so every sexual trill and every horny feeling is because of increased testesteron in the body,by streching the penis,testicals put way more testosterone in the body,so Penis Enlargement in general is one of the best methods to increase testesterone like squats,like fast running like many leg exercises,good balanced diet,tribulis,zinc,zma, Pe also increase testesterone.
p.s You get erect when balls start to produce more testesterone than normal,so people with low testesterone have problem with erections.