Remember those chem lab days? Well, if you do, you may remember that sometimes the concentration of a solvent or chemical is more important than the absolute amount of the same. What I remember even more is getting kicked solidly in the right buttock by my 8th grade chem teacher for goofing around with chemicals in the laboratory, but that's another story.
Again, though, the concentration is often critical and this hold true in the hormonal world as well. For example, researchers recently found that it is the ratio of testosterone to estrogen that determines prostate cancer health more than total testosterone.
So what is a good T/E ratio? A solid number for a 20 year old male is 30-40 with some guys shooting near 50. Of course, some would argue that a T/E ratio that high makes it to where most guys can't think straight. Regardless, youthful testosterone-to-estradiol ratios are quite high and are certainly ideal in terms of maintaining male health.
NOTE: Estradiol is the most powerful estrogen in us guys and is termed E2. Most testosterone-to-estrogen ratios are actually testosterone-to-estradiol ratio in the literature from what I have read, and I use them interchangeably below.
Of course, the problem is that guys, as they age, find this all-important testosterone to estrogen ratio steadily decreasing to sometimes even the single digits. The situation seems hopeless because all males find their testosterone simultaneously decreasing and their estrogen increasing. This is assaulting our T/E fraction in both numerator and denominator: you've got the numerator decreasing while the denominator is increasing. Quite the "double whammy", eh?
NEWS FLASH: A recent study showed that lower testosterone-to-estradiol ratios were actually tied to higher PSA's.  In fact, this study showed that testosterone may actually be protective and estradiol the prime culprit in fueling cancer. See my page on High Estradiol's Links to BPH and Prostate Cancer.
What causes these rapid changes on both top and bottom in the negative direction. Well, some of it is aging. Males just naturally lose a little testosterone as they age due to mitochondrial dysfunction, DNA and oxidative damage and so on. However, one of the greatest culprits is the extra pounds around our middle. Extra fat pumps out more aromatase which in turn pumps out more estrogen into our system.
That creates a viscious cycle because the extra estrogen will "crowd out" testosterone and lower the body's testosterone output. Then, as testosterone is lowered, muscle is lost and as muscle is lost, fatty tissue is increased and so on.
Is there any good news in all of this? Yes, the same "double whammy" that lowers our T/E ratio can also raise it. Below we cover three excellent ways to dramatically improve your testosterone-to-estrogen ratio:
1. Body Fat. Of course, it's not secret that body fat and male estrogen levels go hand-in-hand. Many studies show this, but let's look at one study of guys with fertility problems. These were relatively young guys within a decade on either side of the average age of 39. They split them up into two groups: those with a BMI > 25 and those with a BMI less than 25. The difference in testosterone-to-estrogen ratios was signficantly different: 12 versus 17. That is a 42% difference!
Does this make sense that body fat would make such a significant difference in the T/E ratio? Remember that the more fat, the more aromatase and the more aromatase the more estrogen and the more estrogen, the less testosterone. Excess body weight is correlated with both lowered testosterone and increased estrogen. In other words, being overweight will hit both sides of the fraction negatively.
By the way, this may explain why weight lifting has been associated with increased long term testosterone levels. Weight will increase muscle mass and "muscle burns fat". Adding muscle, however you do it, will actually change your metabolism for the better so that the same calories go farther.
Did you know you can inexpensively do your own testing for most hormones? The industry leader is Discounted Labs..
And I should add that some men, generally obese, can experience MONSTROUS increases in testosterone by losing lots of weight (once the restore their calories). The reason is that obesity can lead to a type of secondary hypogonadism where the signaling from the hypothalamus-pituitary-testes axis gets dramatically reduced.
2. Low Fat Diet. Most men believe that a Low Fat Diet is very negative for your endocrine profile and, in particular, will devastate testosterone. However, preliminary evidence shows just the opposite. One small study found that estradiol (the "bad" estrogen or E2) fell from 47.2 to 23.8 pg/ml on average, which is obviously a big change. This is a reduction of over 50% and cut their estrogen levels in half!  And the remarkable thing is that their testosterone stayed steady before and after at 510 ng/dl.
It is true that for some men, they may experience a slight reduction in total testosterone levels by going on a Low Fat Diet depending on how they have been eating. However, what most men do not know is that they will likely experience a very significant improvement in their all-important testosterone-to-estrogen ratio. This is what many of your tissues really care about: how many "male" hormones you have floating around versus "female". The more male hormones you have proportionately, the more those receptors will get activated after all. (See my link on the Testosterone-to-Estrogen Ratio for more details.)
And what a difference a Low Fat Diet can make! One study examined the hormones of 21 males who went on a Lowf Fat Diet and found that there estradiol (the "bad" estrogen or E2) dropped from 47.2 to 23.8 pg/ml on average. This is a reduction of over 50% and effectively halved their estradiol levels.  And the remarkable thing is that their testosterone stayed constant at 510 ng/dl!) This means that their testosterone-to-estrogen ratio was effectively doubled just by this simple dietary change. For additional information, see my link on Low Fat Diets and Testosterone.
Increasing your T/E Ratio by a factor of 2+ should grab every man's attention, especially considering it was done simply by diet. Check out The Incredible Benefits of a Low Fat Diet.
3. Sexual Intercourse (via Cialis). As an example, let's look at an eye-opening Cialis study. Of course, Cialis is the 36-hour PDE5 inhibitor that has put so many middle-aged and beyond guys back in the game. And getting back into the game has a profound effect for most much guys: it boosts their testosterone to estrogen ratio by 24% on average according to one study. 
The reason? Cialis gives guys who are struggling confidence and that all-important Nitric Oxide boost that leads to more sex. And more sex boosts testosterone and a host of other changes. What is interesting is that in the above study, testosterone only increased 5.5% on average but estrogen lowered by about 15%. And the net boost in the T/E ratio exceed the sum of those two by a few percentage points as well.
Now this is a remarkable change if you think about it. The "concentration" of testosterone and estrogen - estradiol is what really counts - changed by 24% from just one lifestyle change. Imagine what could happen as you pile on some of the other Testosterone Increasing Techniques and Estrogen Lowering Strategies that I have mentioned on the web site. There is no reason that you cannot dramatically improve your ratio of testosterone to estradiol (unless you happen to be training for the Olympics with a professional trainer).
4. Arimidex. Arimidex (anastrolozole) is an aromatase inhibitor that, not too surprisingly, can do wonders your T/E ratio. It works by actually binding to the aromatase enzyme that converts testosterone to estrogen. And if you want to best your testosterone-to-estradiol ratio, it's hard to beat. For example, one study showed that in hypogonadal senior men, the T/E ratio was increased on average by 115%! It produced a 62% in testosterone and a 24% decrease in estradiol.  Of course, it is a pharmaceutical and thus has side effects and unknown long term safety. But it's hard to argue against its great hormonal properties. NOTE: Other AI's (aromatase inhibitors) can produce similarly spectaculr changes in the testosterone to estrogen ratio as well. For example, one study showed Teslac (testolactone) also produced an improvement of over 100%. 
The point is that, at least using #1-#2, you can use some very natural strategies that will very likely make a very substantial change to your testosterone/estrogen ratio and, as a consequence, feel much better and lower your risk for many diseases and conditions.
CAUTION: Most guys probably do not know that caffeine increases both cortisol AND testosterone. Unfortunately, it does not raise testosterone enough proportionately thus lowering the overall testosterone-to-estrogen ratio. 
1) The Journal of Sexual Medicine, Jul 2006, 3(4):716-722, "Testosterone:Estradiol Ratio Changes Associated with Long-Term Tadalafil Administration: A Pilot Study"
2) Systems Biology in Reproductive Medicine, 2006, 52(2):97-102, "EFFECT OF BODY WEIGHT ON TESTOSTERONE/ESTRADIOL RATIO IN OLIGOZOOSPERMIC PATIENTS"3) Int J Sport Nutr Exerc Metab, 2008 Apr, 18(2):131-41, "Dose effect of caffeine on testosterone and cortisol responses to resistance exercise"
3) Am J Med, 1985 Jan, 78(1):23-7, "Effects of a high-complex-carbohydrate, low-fat, low-cholesterol diet on levels of serum lipids and estradiol"
4) Clin Endocrinology, 2009, vol. 70(1)"116-123, "Effects of aromatase inhibition in hypogonadal older men : a randomized, double-blind, placebo-controlled trial"
5) The Journal of Urology, Feb 2002, 167(1):624-629, "AROMATASE INHIBITORS FOR MALE INFERTILITY"
6) Indian J Clin Biochem, 2015 Jan, 30(1):59-65, "Serum Testosterone, 17Î²-Estradiol and PSA Levels in Subjects with Prostate Disorders"