1. Genes
2. Aging
3. Lifestyle
I would rank cause of low T in that order. Found out I had low T 2 years ago after complaining to my MD's for 15 years of the symptoms. Had 2 older brothers check theirs and also my son and all 3 had low T so, its obviously IMO a genetic trait on the male side of my family.
My Dad died at 72 of colon cancer, older cousins and Uncles died of same thing at an early age. All my Aunts on my Dad's side of the family all lived to their 90's, fairly healthy and active.
