A study in a large primary care patient population shows that low baseline testosterone in women aged 43-72 years is associated with increased all-cause mortality and cardiovascular events. This association was found to be largely independent of traditional risk factors, and supports the notion that the hormonal status in middle age and older women might impact morality outcomes.
The objective of the study was to determine whether baseline testosterone levels in women are associated with future overall or cardiovascular morbidity and mortality.
Hypogonadism, aka testosterone deficiency or low-T, is primarily diagnosed by low total testosterone levels. However, more and more research is showing that free testosterone, which is the active fraction of total circulating testosterone, is independently associated with important health outcomes.
Levels of free testosterone decline more steeply than total testosterone as menage.[1-7 In many cases, total testosterone levels can be relatively high, but free testosterone low. Therefore it is important to assess both total and free testosterone levels in order to get a clear picture of the androgen status.
A recent study specifically assessed if baseline testosterone (total and free) levels predict muscle loss in middle-aged and elderly Japanese men over a 10 year period.
Low levels of testosterone in men may contribute the development of insulin resistance and diabetes.[1-4] However, few studies have examined the association between testosterone levels and diabetes in men in the general population.
An interesting study was cunducted to test the hypothesis that low normal levels of total, free, and bio-available testosterone are associated with prevalent diabetes in men.
Recent evidence strongly suggests that testosterone deficiency is a predisposing factor for various chronic illnesses, including cardiovascular disease, diabetes and osteoporosis.[1-3]Testosterone deficiency has also been implicated as a modifiable disease risk factor for various chronic diseases in otherwise well patients.[4-7]
Cardiovascular disease, diabetes and osteoporosis-related fractures consume a significant portion of the $2.3 trillion in annual U.S. health expenditures. The economic impact of diabetes is estimated at $503 billion, $152 billion for cardiovascular disease, and $6 billion for osteoporosis-related fractures.[8-10]
Thus, the total burden of these diseases is over $660 billion, representing approximately 29% of all U.S. health care expenditures in 2008. Since testosterone deficiency is a potentially modifiable risk factor for these and other medical conditions, it may be responsible for substantial financial and quality-of-life burden on the U.S. health care system.
A study was conducted to specifically quantify the cost burden imposed by consequences of testosterone deficiency ...
The consequences of low testosterone levels (aka low-T) have been primarily investigated in middle-age and older men. However, low-T in young men aged 20-39 years can confer health risks as well...
Low total testosterone levels are associated with an adverse blood lipid profile, which includes high TG and low HDL, [1, 2] and a decline in total testosterone levels predisposes men to increased risk of cardiovascular disease (CVD) and mortality.[3-7]
Prediabetes is a condition in which blood glucose level is higher than normal but does not reach the level for diabetes diagnosis.[1, 2] Studies have shown that people with prediabetes tend to develop type 2 diabetes within 10 years, and are at increased risk for cardiovascular disease.
Among US adults over 18 years, the prevalence of prediabetes has increased from 29.2% in 1999 to 36.2% in 2010. Considering the entire US population in 2010 (approx. 309 million, data from US Cencus), this corresponds to 112 million US adults, or over one third of the US population.
Data from non-diabetic men have revealed an inverse association between insulin resistance and testosterone levels; i.e. a higher degree of insulin resistance is associated with lower testosterone levels.[4-6] This raises the question whether prediabetes, which is a state of increased insulin resistance, is also associated with low testosterone. However, few studies have investigated testosterone levels in men with prediabetes, and the risk of testosterone deficiency in men with prediabetes has not been reported.
Because the prevalence of prediabetes is affecting such a large number of Americans, and is on the rise, it is important to investigate how this condition might affect testosterone levels. Knowing that can help
detect men who are likely to have testosterone deficiency and might be at risk for health derangements caused by low-T.
It is well-documented that testosterone levels decline with age in men.
After the age of 40 years, total testosterone decreases on average -4 ng/dL ( -0.124 nmol/L) per year  or 1.6% per year , and bioavailable testosterone by -2 to 3% per year. 
In older men (over 60 years of age), the average rate of decrement in total testosterone levels has been found to be 110 ng/dL every decade.
However, the relative contributions of changes in health and lifestyle to that decline have not been adequately evaluated. A notable study was set out to investigate this...
The objective of this study was to establish the relative importance of aging, health, and lifestyle in contributing to the testosterone decline in aging men.
A notable study shows that men aged 20–79 who have low testosterone levels below 8.7 nmol/L (250 ng/dL) have a more than two-fold increased risk of mortality from all causes, compared with those with higher serum testosterone levels.
Importantly, this risk is independent of age, waist circumference, smoking habits, high-risk alcohol use, and physical activity.
March 6th 2014 FDA approved Aveed for treatment of male hypogonadism, aka testosterone deficiency. Aveed is a long-acting form of injectable testosterone called testosterone undecanoate. In Europe, testosterone undecanoate (under the name Nebido) has a long successful TRT track record for treatment of testosterone deficiency and its consequences (especially obesity, the metabolic syndrome and diabetes).[2-16]
In contrast to shorter acting forms of testosterone (e.g. cypionate), testosterone undecanoate only needs to be injected every 6 to 12 weeks, and thereby offers practical benefits to patients. (Comment: for Nebido (1000 mg per 4 ml) the initial interval is 6 weeks, followed by intervals of 10-14 weeks; for Aveed (750 mg per 3 ml) the initial interval is 4 weeks, followed by 10-week intervals).
Five days after the FDA approval a notable and impressive 6-year long TRT study was published, confirming the health benefits of TRT that have previously been found in shorter term studies... 
We previously posted a commentary on the recently published and notoriously flawed study which concluded that TRT increases risk for heart attack.
This is the study which caused the media debates:
January 29th issue, the Scientific Journal PLOS (Public Library of Science) ONE published the article:
Here we have gathered commentaries from other medical professionals, all in one place:
- Testosterone Replacement Therapy (TRT) in Testosterone Deficient men - effects on fat loss, waist reduction and metabolic syndrome components
- Does Testosterone Therapy Really Increase the Risk of Heart Attack?
- Is testosterone a friend or a foe of the prostate?
- Testosterone Replacement Therapy - why is it so controversial?