Attention, memory, and spatial ability are key cognitive functions affected by testosterone in humans. Preliminary evidence suggests that low testosterone levels may be a risk factor for cognitive decline and possibly for dementia of the Alzheimer's type,[100][101][102][103] a key argument in life extension medicine for the use of testosterone in anti-aging therapies. Much of the literature, however, suggests a curvilinear or even quadratic relationship between spatial performance and circulating testosterone,[104] where both hypo- and hypersecretion (deficient- and excessive-secretion) of circulating androgens have negative effects on cognition.
According to the Mayo Clinic, testosterone therapy can help treat hypogonadism. This condition occurs when the body can’t produce enough testosterone on its own. However, it’s unclear whether supplements can help. A study published in Nature Reviews Endocrinology found no scientific reason to prescribe testosterone to men over 65 years of age with normal or low to normal testosterone levels.
Testosterone boosters are used by many athletes worldwide to achieve a significant muscle mass increase within a short period of time.[1] However; one cannot be completely confident in terms of the quality and efficacy of such products because of several reasons, such as the possibility of bad storage conditions and originating from an unreliable source. Over the years, some consumers of testosterone boosters have complained of kidney and liver abnormalities that could be linked to their use of boosters.[10] Cases of erroneous product administration have occurred in the past as athletes may not follow the instructions on the label fully, which can lead to many side effects.[11] In the present case, a man was admitted to a hospital because of a severe abdominal pain. The pain was later found to be caused by liver injury. The diagnosis confirmed that the levels of the key hepatic enzymes were markedly elevated. The medical complications observed were found to have occurred following the consumption of two courses of a commercial testosterone booster. According to researchers based in the US, about 13% of the annual cases of acute liver failure are attributable to idiosyncratic drug- and/or supplement-induced liver injury.[12] Marked increase in the levels of ALT, AST, and gamma-glutamyl transferase was observed after consuming the first course of the commercial testosterone booster, and they started to decline after the 2nd and 3rd course. This abruptly increases the levels of liver enzymes after the first course may be attributed to the interruption effect of commercial testosterone booster on liver function as a result of the effects of its ingredients.
Mental status changes including excess aggression are a well known phenomenon in the context of anabolic steroid abuse (Perry et al 1990). An increase in self-reported aggressive behaviors have also been reported in one double blind placebo controlled trial of testosterone in young hypogonadal men (Finkelstein et al 1997), but this has not been confirmed in other studies (Skakkebaek et al 1981; O’Connor et al 2002). Aggression should therefore be monitored but in our experience is rarely a significant problem during testosterone replacement producing physiological levels.

I was reading in the university health news daily website that a study performed by researchers at the University of Texas M.D. Anderson Cancer Center found that men with prostate cancer who ate 3 tablespoons of milled or ground flax seeds each day had decreased prostate cancer cell proliferation compared to similar men who did not eat flax seeds. According to the American Cancer Society, men who supplement their diets with flax seed have lower PSA levels and slower growth of benign as well as cancerous prostate cells.
Some of these signs and symptoms can be caused by various underlying factors, including medication side effects, obstructive sleep apnea, thyroid problems, diabetes and depression. It's also possible that these conditions may be the cause of low testosterone levels, and treatment of these problems may cause testosterone levels to rise. A blood test is the only way to diagnose a low testosterone level.