Testosterone may decrease your chances of Alzheimer’s Disease. Several studies have linked low testosterone levels to an increased risk of Alzheimer’s disease.  In a 2010 study by the University of Hong Kong, researchers studied 153 Chinese men who were recruited from social centers. They were at least 55 years and older, lived in the community, and didn’t have dementia. Of those men, 47 had mild cognitive impairment — or problems with clear thinking and memory loss.
There are several supplements on the market claiming to be natural testosterone boosters. I get these sorts of things in the mail all time. The companies that produce these products claim that the herbs (typically stinging nettle and tribulus) in their pills increase free testosterone by reducing SHBG. They also throw in some B vitamins for “increased energy and vitality.”
Dr. Resnick and colleagues assessed 788 participants in the cognitive function arm of the TTrials but focused on the 493 participants who were classified as having age-associated memory impairment with a confirmation of both subjective and objective indicators of cognitive decline. The authors detected no significant effect after 1 year of testosterone treatment on either the primary outcome of verbal memory, as measured by delayed paragraph recall or on any of the secondary outcomes of visual memory, executive function, and spatial ability.1
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.