Getting back to natural levels of hormone.
Most of what we're experiencing as far as a drop in our natural production appears very much to be the result of the environment.
You gotta keep in mind the testes produce 95% of your testosterone and those leydig cells are extremely sensitive to all sorts of chemicals. Also viruses can cause problems as well, like my T production that plummeted after I had a nasty bout with mononucleosis that cooked me with a 107 fever.
I'd be more interested to see what natural T levels are in identical twins, where one is raised in our modern world and one is raised in a natural environment free from all modern toxins.
Aside from that:
1. Low body fat, means less aromatase coverting T to estrogen.
2. High intensity training of no more than 45 minutes a day with max reps of 12 to prevent cortisol from over training. More muscle mass means more natural GH and T production.
3. Sleep. REM sleep is where nocturnal T is produced.
4. Diets that are well balanced and not heavy with protein. It appears that diets too high in protein >35% can drop natural T, this goes back to commonsense when people ate balanced diets and not these fad diets. Making sure the diet is rich in micronutrients of zinc, Vit A and D. Fish, Red meat, sweet potatoes, colorful veggies.
Obviously if a guy has a 1000 ng/dl natural levels then they hit the jackpot and should do everything to take care of preserving that for life. Most of us like myself came to anabolics only after we had really good years of natural production where we saw our progress suddenly drop off and we went looking for answers.