The second theory is similar and is known as "evolutionary neuroandrogenic (ENA) theory of male aggression".   Testosterone and other androgens have evolved to masculinize a brain in order to be competitive even to the point of risking harm to the person and others. By doing so, individuals with masculinized brains as a result of pre-natal and adult life testosterone and androgens enhance their resource acquiring abilities in order to survive, attract and copulate with mates as much as possible.  The masculinization of the brain is not just mediated by testosterone levels at the adult stage, but also testosterone exposure in the womb as a fetus. Higher pre-natal testosterone indicated by a low digit ratio as well as adult testosterone levels increased risk of fouls or aggression among male players in a soccer game.  Studies have also found higher pre-natal testosterone or lower digit ratio to be correlated with higher aggression in males.     
Dear Dr Miller, myself and my wife we were trying to have baby since last 3 yrs but no success. Last month i went to doctor and had my FSH,LH,T and SA tests done. FSH – uIU/ml, LH – uIU/ml, T – ng/ml. Sperm count was M/ml. Doctor told me that LH and T are normal where as FSH is high. He suggested me to take clomid 25mg daily to increase my sperm production . After 1 month , i had done my SA tests again . i expected sperm count to increase but instead i found out that my sperm count has actually decreased to M/ml. Pls help me doctor
So we know we don't want to go too low with estradiol or we could end up with brittle bones and hip fractures like a lot of 75 year old women struggle with. Furthermore, common sense dictates that more is not better when it comes to estradiol. Many men who go on HRT and end up with estradiol in the 40's and 50's very commonly have a certain suite of side effects: gyno, water retention, lowered libido, loss of erectile strength, moodiness, poor sleep etc. If you've been around Peak Testosterone Forum at all, you know this is actually quite common. And many experts have concern about long term effects as well, because high estradiol may increase clotting risk, arterial plaque and prostate issues as I mentioned.