In addition to its role as a natural hormone, testosterone is used as a medication, for instance in the treatment of low testosterone levels in men and breast cancer in women.[10] Since testosterone levels decrease as men age, testosterone is sometimes used in older men to counteract this deficiency. It is also used illicitly to enhance physique and performance, for instance in athletes.
It has also been found that college graduates with higher levels of T (men and women alike) are more likely to go into riskier careers. Another study discovered that among financial traders, a trader’s morning level of testosterone accurately predicted his day’s profitability – higher levels of T mean he’s more likely to take risks that day and score big.

Mood disturbance and dysthymia are part of the clinical syndrome of hypogonadism. Epidemiological studies have found a positive association between testosterone levels and mood, and depressed aging males have lower testosterone levels than controls (Barrett-Connor, Von Muhlen et al 1999). Furthermore, induction of a hypogonadal state during treatment of men for prostate cancer leads to an increase in depression scores (Almeida et al 2004). Trials of testosterone treatment effects on mood have varied in outcome. Data on the effects on men with depression are conflicting (Seidman et al 2001; Pope et al 2003) but there is evidence that testosterone treatment of older hypogonadal men does result in improvements in mood (Wang et al 1996) and that this may occur through changes in regional brain perfusion (Azad et al 2003).

Two of the immediate metabolites of testosterone, 5α-DHT and estradiol, are biologically important and can be formed both in the liver and in extrahepatic tissues.[155] Approximately 5 to 7% of testosterone is converted by 5α-reductase into 5α-DHT, with circulating levels of 5α-DHT about 10% of those of testosterone, and approximately 0.3% of testosterone is converted into estradiol by aromatase.[2][155][161][162] 5α-Reductase is highly expressed in the male reproductive organs (including the prostate gland, seminal vesicles, and epididymides),[163] skin, hair follicles, and brain[164] and aromatase is highly expressed in adipose tissue, bone, and the brain.[165][166] As much as 90% of testosterone is converted into 5α-DHT in so-called androgenic tissues with high 5α-reductase expression,[156] and due to the several-fold greater potency of 5α-DHT as an AR agonist relative to testosterone,[167] it has been estimated that the effects of testosterone are potentiated 2- to 3-fold in such tissues.[168]
   The International Journal of Sports Physiology and Performance recently studied tennis players, rugby teams, and wrestlers to find a link between testosterone and competitive outcome. They found that the difference between winning and losing was reflected in testosterone levels! The athletes' own natural testosterone prior to the game was directly related to the outcome after the game -- the higher the testosterone, the more frequently the athlete won.6

The Organon group in the Netherlands were the first to isolate the hormone, identified in a May 1935 paper "On Crystalline Male Hormone from Testicles (Testosterone)".[184] They named the hormone testosterone, from the stems of testicle and sterol, and the suffix of ketone. The structure was worked out by Schering's Adolf Butenandt, at the Chemisches Institut of Technical University in Gdańsk.[185][186]

I am 35 and had the non sexual symptoms for awhile now( weight gain/muscle loss, extreme fatigue, lack of clarity/concentration) I got my testosterone levels checked last week and it was 35.4 ng. Not a typo, 35.4. I was told by my dr. That I needed to start TRT right away as low t can effect a lot different things in your body. I did my first injection last night (200mg/ml every 2 weeks) about 8 pm and td now 3:30 am and I’m wide awake and feel extremely motivated to go to the gym and work out. I know each person is different but should I feel like this already, or is it a placebo effect at this point?
Boron, a mineral, keeps the cell walls of plants strong. Eating dried fruits and nuts gives you abundant amounts of boron. You can also take boron supplements. It's important to keep your daily boron intake at less than 20 mg, however, according to a current factsheet available from the U.S. National Library of Medicine. High doses of boron can cause serious side effects such as skin inflammation and peeling, irritability, tremors or depression.

The regular intake of testosterone boosters is known for the high level of safety comparing to the hormone injections and the use of illegal steroids. But still to protect yourself against any possible adverse reactions, you should remember that the supplementation can’t be continuous. The breaks from time to time are required. Such an approach to the use of boosters is healthy and best-working if you aspire to enhance own hormone production without any harm.
If a young man's low testosterone is a problem for a couple trying to get pregnant, gonadotropin injections may be an option in some cases. These are hormones that signal the body to produce more testosterone. This may increase the sperm count. Hedges also describes implantable testosterone pellets, a relatively new form of treatment in which several pellets are placed under the skin of the buttocks, where they release testosterone over the course of about three to four months. Injections and nasal gels may be other options for some men.