The largest amounts of testosterone (>95%) are produced by the testes in men,[2] while the adrenal glands account for most of the remainder. Testosterone is also synthesized in far smaller total quantities in women by the adrenal glands, thecal cells of the ovaries, and, during pregnancy, by the placenta.[126] In the testes, testosterone is produced by the Leydig cells.[127] The male generative glands also contain Sertoli cells, which require testosterone for spermatogenesis. Like most hormones, testosterone is supplied to target tissues in the blood where much of it is transported bound to a specific plasma protein, sex hormone-binding globulin (SHBG).
Michael T. Murray, ND, is widely regarded as one of the leading authorities on natural medicine. He is the author of many books, including the classic Encyclopedia of Nutritional Supplements. His latest book is What the Drug Companies Won’t Tell You and Your Doctor Doesn’t Know. Visit him online at doctormurray.com.   Article Courtesy of Better Nutrition  
A notable study out of Wayne State University in Indiana found that older men who had a mild zinc deficiency significantly increased their testosterone from 8.3 to 16.0 nmol/L—a 93 percent increase—following six months of zinc supplementation. Researchers of the study concluded that zinc may play an important role in modulating serum testosterone levels in normal healthy men.6
For example, the study published in Obesity Research tells that the scientists measured testosterone levels in two groups of middle-aged men with obesity. One group underwent a 16-week weight loss program, while the second group did nothing. Each participant of the first group lost 20 kg on the average. And these participants experienced a significant increase in testosterone levels. So, the fight against overweight is very important for those who want to overcome testosterone deficiency. But starvation is strictly forbidden because this is a stressful situation which leads to the sharp decline in T levels.
If you are serious about losing weight, you have got to strictly limit the amount of processed sugar in your diet, as evidence is mounting that excess sugar, and fructose in particular, is the primary driving factor in the obesity epidemic. So cutting soda from your diet is essential, as is limiting fructose found in processed foods, fruit juice, excessive fruit and so-called "healthy" sweeteners like agave.

Although the benefits of multivitamins are hotly debated, specific vitamins and minerals may be beneficial. In one study, zinc and vitamin B supplements increased sperm quality by 74%. Zinc also boosts testosterone in athletes and those who are deficient in zinc. Other studies also suggest vitamins A, C and E can play a role in your sex hormone and testosterone levels, although more research is needed. Out of all the vitamins and minerals available, the research on testosterone shows vitamin D and zinc supplements may be best.
The biggest problem with supplementing your testosterone levels is it can shut off your own natural production and it can also permanently lower your sperm count. Taking testosterone boosters may also leave you open to some of the other unwanted side effects, like acne, male pattern baldness, mood swings and aggressive behaviour. To give yourself the best possible chance of avoiding these side effects, you need to see an expert before going for boosters.
Early infancy androgen effects are the least understood. In the first weeks of life for male infants, testosterone levels rise. The levels remain in a pubertal range for a few months, but usually reach the barely detectable levels of childhood by 4–7 months of age.[15][16] The function of this rise in humans is unknown. It has been theorized that brain masculinization is occurring since no significant changes have been identified in other parts of the body.[17] The male brain is masculinized by the aromatization of testosterone into estrogen, which crosses the blood–brain barrier and enters the male brain, whereas female fetuses have α-fetoprotein, which binds the estrogen so that female brains are not affected.[18]
Zinc is little more of a nice-to-have ingredient than a must-have. It’s on our radar as an ingredient that possibly boosts testosterone levels, and while we couldn’t find enough supporting evidence that taking zinc would increase natural testosterone, low zinc levels have been connected to infertility. A low zinc level is also possibly a sign of hypogonadism. The closest support we found is in a study which found that people recovered from nutritional deficiency-related problems more quickly if they took a zinc supplement than those who did not. Zinc is available in many foods, such as oysters, fortified breakfast cereals, and red meat.

Sexual arousal - boosting testosterone can improve sexual arousal, even if you have normal testosterone levels. Higher levels of testosterone can make it easier for you to get aroused and can boost your sex drive generally. While this doesn’t affect the physical action of your erections, if you are not getting hard because you’re not aroused then boosting testosterone could help.
Both Beast Sports’ Super Test and iSatori’s ISA-Test contain a proprietary blend, which means they don’t disclose the amount of each and every ingredient in the mix. This is only a problem if there is an ingredient tucked into a proprietary blend for which we need to know an amount, like magnesium and zinc. While none of the ingredients in Beast Sports’s proprietary blend raised any red flags, iSatori’s blend contains melatonin, a hormone that helps regulate sleep. Melatonin is an ingredient that has a hard upper limit — Healthline suggests at most 10mg for an adult — and even lower doses can interact poorly with many medications. Since we can’t confirm whether the amount of melatonin in iSatori’s proprietary blend is under 10mg, we cut iSatori.

Sharma, R., Oni, O. A., Gupta, K., Chen, G., Sharma, M., Dawn, B., … & Barua, R. S. (2015, August 6). Normalization of testosterone level is associated with reduced incidence of myocardial infarction. European Heart Journal, 36(40), 2706-2715. Retrieved from https://academic.oup.com/eurheartj/article/36/40/2706/2293361/Normalization-of-testosterone-level-is-associated
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