As we learn more about the health effects that are associated with low testosterone (defined as less than 300 nanograms per deciliter of blood), it is apparent that the impacts upon the health of most men range from being asymptomatic, to serious health conditions such as congestive heart failure, or cumulative and serious vision impairments.
It is not clear yet, whether the low levels of testosterone in the blood are causing these issues, or whether they are effects of other health problems. I tend to agree with the hypothesis that low and ultra-low testosterone are causative , and left untreated, can cause serious disease processes.
In men of a certain age such as I (over 40), to an elderly man, low testosterone can result in fatigue, moodiness, depression, inefficient use of nutrients along with other issues. It is important to use a blood test to check on testosterone levels in any cases where a man has developed symptoms. Important enough that it can carry the weight of a life or death decision. Men with ultra low testosterone are just over 40% more likely to have a heart attack than men who have levels at, or well above the normal level.
The discovery of a blood testosterone level that is far below normal can also be a tipoff that the endocrine system is generally having problems. In my own case, the onset of Ankylosing Spondylitis (I wouldn't know that I had AS until nearly eight years later), both because it is the result of my immune system attacking healthy joints and connective tissue, and because it causes inflammation throughout the body, occurred at the same time, I began feeling a deep fatigue. This fatigue was not only feeling "tired". but was an indicator that something in my body was failing. I am fortunate to have a primary care physician named Warren Fein, a man who is not only very good at his job, but is an excellent listener. When he heard my description of the fatigue, he immediately checked for blood thyroid levels, and when they were low (well below the minimum threshold), he prescribed a synthetic thyroid replacement, then followed up to see if my fatigue had abated. It had not, and this caused us to set out on a mission to find the rest of the problems, if any, with my endocrine system.
In my case, not only had my thyroid been affected, but I also had low vitamin D levels, low testosterone, elevated cortisol, low human growth hormone, etc. In other words, we learned that there were so many areas of the endocrine system that were out of whack, both Dr. Fein and I believed that something was causing the pituitary system to fail. Even after beginning testosterone replacement therapy following an evaluation with Dr. Davies ( a top-notch endocrinologist), my blood levels continued to decline - at one point I had only 70 nanograms per deciliter of blood. finally, with larger doses every other week, we were able to get the testosterone level up to just over 300.
I encourage men over 40 to read up on the issue and if you are experiencing some symptoms which could be related to low T, discuss it with your doctor. You might just be saving your own life.