Testosterone, often dubbed the male hormone, plays a crucial role in overall quality of life beyond just libido. What many may not realize is that testosterone levels have been steadily declining across generations, and conventional reference ranges have followed this downward trend.
At Superpower, we rely on emerging clinical research to establish a higher, and narrower optimal range. This approach avoids underdiagnosing deficiencies and ensures early intervention for the best possible health outcomes, extending well beyond sexual health.
Key Points
- Generational Decline: Testosterone levels have been falling across generations. This decline has been reflected in current ranges, which may represent suboptimal levels.
- Flawed Reference Ranges: The current range (300-1000 ng/dL) is too broad and fails to diagnose deficiency, which could occur at levels within the “normal” range.
- “Normal” is not “Optimal”: Our range of 600-900 ng/dL is better aligned with diagnosing deficiency early to ensure better outcomes in cardiometabolic health, body composition, and longevity.
- Conventional Range
- Total Testosterone: 300 - 1000 ng/dL
- Total Testosterone: 5 – 25 pg/mL
- Superpower Optimal Range
- Total Testosterone: 600 - 900 ng/dL
- Free Testosterone: 15 - 25 pg/mL
What is Testosterone?
Testosterone is a sex hormone and often referred to as the “male hormone”. While primarily produced in the testicles in men, it's also made in smaller amounts in women's ovaries and adrenal glands [1, 2].
Once released into the bloodstream, most testosterone attaches to proteins like albumin and sex hormone-binding globulin (SHBG), which transport it throughout the body. Around 40% of your testosterone will be loosely attached to albumin, while a small portion will remain unbound - this known as "free testosterone" [3]. The unbound and albumin-bound testosterone are more "bioavailable", meaning they're readily accessible for the body's use. The sum of all three forms —SHBG-bound, albumin-bound, and free -- is known as "total testosterone" [3].
What is the function of testosterone?
Testosterone's influence extends far beyond its well-known role in sexual function and libido – your interest in sex [4]. With testosterone receptors present throughout the body, this hormone significantly impacts both male and female physiology [5].
In men, testosterone is essential for reproductive development [4]. It drives the growth of the testes and prostate, and promotes secondary sexual characteristics during puberty. These include increased muscle and bone mass, deeper voice, and growth of body hair. Testosterone also stimulates sperm production, maintaining male fertility [2, 6].
Beyond reproduction, testosterone influences body composition by regulating the distribution of fat and enhancing muscle strength [7, 8]. In bones, testosterone stimulates mineral accumulation, increasing density which prevents brittle bones in conditions like osteoporosis [9]. Testosterone also supports the production of red blood cell in the bone marrow, which is vital for oxygen delivery [10, 11]. Moreover, testosterone also strengthens the blood vessels networks used to deliver the oxygen-rich blood [12, 13].
In the brain, testosterone strengthens the nerve networks contributing to brain function, memory, and special skills [14-16]. It also aids in balancing your mood by regulating serotonin and boosting dopamine, the brain’s “feel-good” chemicals [17, 25, 26]. Lastly, testosterone plays a crucial role in regulating men's sleep patterns and quality, while good sleep in turn boosts testosterone production [27, 28].
As we age, testosterone levels progressively fall and trigger significant changes to the body, including loss of muscle, weakened bones, altered fat storage, and insulin resistance—creating the perfect conditions for the onset of metabolic syndrome [18-22].
What is the conventional reference range?
The conventional reference range for total testosterone varies between labs, but typically falls within:
- Conventional Range for Total Testosterone: 300 - 1000 ng/dL
- Conventional Range for Total Testosterone: 5 – 25 pg/mL
This range is based on population averages, including men with suboptimal levels. Consequently, it may lead to under-diagnosis of testosterone deficiency in men who fall within the "normal" but still suboptimal range [23, 24].
Due to sex-specific differences between the concentration and function of testosterone, these ranges are optimised for MALES. To learn more about testosterone for FEMALES click here.
What is the Superpower Optimal Range for Testosterone?
At Superpower, we recommend more precise optimal ranges for total testosterone:
- Superpower Optimal Range (Total Testosterone): 600 - 900 ng/dL
- Superpower Optimal Range (Free Testosterone): 15 - 25 pg/mL
Our optimal ranges focus on levels that maximize well-being, based on clinical research showing better health outcomes at higher levels.
When assessing testosterone levels, it's important to also consider DHEA and SHBG levels. DHEA can influence overall sex-hormone activity, while SHBG affects how much free testosterone is available for your body to use.
Why is the Conventional Range for Testosterone Problematic?
The conventional reference range, typically defined as 300-1,000 ng/dL, is problematic because it is intended to diagnose severe testosterone deficiencies, such as hypogonadism, rather than support optimal physiological function.
Research shows a consist historic decline in testosterone [29-35]. As levels have been declining across generations, the reference ranges have adjusted downward to reflect this trend. This means that what is now considered "normal" might represent suboptimal levels when compared to historical norms. Consequently, men with testosterone levels within the lower end of this range might experience health issues that would have been preventable had the reference range been anchored to optimal, rather than “average” levels.
The lower threshold of the conventional reference range corresponds to the 2.5th percentile of the population, meaning that it is will only exclude the most severe cases of testosterone deficiency [24].
Research has shown that men with testosterone levels between 300-400 ng/dL – lower end of “normal”, are more likely to experience adverse health outcomes [36].
Testosterone below 300 ng/dL is linked to poor metabolic health. Studies show the lower end of “normal” is associated with unfavourable fats profiles, higher short and long-term blood sugar, insulin resistance, and lower "good" cholesterol [37]. A study of 70,000+ men found that as testosterone levels dropped below 575 ng/dL, the risk of type 2 diabetes increases. Men with testosterone below 300 mg/dL also tend to have higher body weight, more abdominal fat, and poor physical performance [38].
Men with testosterone levels below ~500 ng/dL also face a higher risk of heart problems [12, 13, 39]. In men with heart failure, testosterone levels ~300 ng/dL correlated with lower blood protein levels, increased inflammation, and higher mortality rates [40]. Moreover, low testosterone was linked to slower blood flow – an accurate predictor of heart health, while levels above 632 ng/dL appeared most beneficial [41].
Testosterone levels independently predict death from all causes. When total testosterone falls below ~250 ng/dL, the risk of all-cause mortality doubles [42].
Men with testosterone levels in the lower end of "normal" already exhibit symptoms of testosterone deficiency which are not adequately addressed as they are within the "normal" range.
Supporting Evidence from Research Studies
Testosterone levels within the range of 600-900 ng/dL have been linked to several important health benefits. For heart health, keeping testosterone levels above 548 ng/dL has been associated with a lower risk of heart attacks and strokes. When testosterone is in the upper half of the normal range (600-900 ng/dL), it's linked to better overall health outcomes, including a lower risk of dying from any cause [24, 43]. In men with heart failure, those with higher testosterone levels within this optimal range had a much lower risk of death, suggesting a protective effect [44].
For physical function and sexual health, testosterone levels between 600-900 ng/dL generally lead to better outcomes. Men within this range tend to have more muscle mass, stronger bones, and better sexual function. Those with lower levels are more likely to experience physical weakness, frailty, weight gain, and problems with sugar metabolism [36, 45, 46]. Keeping testosterone levels in the 600-1000 ng/dL range has also been shown to improve body composition, leading to more lean muscle, less fat, and greater upper body strength, especially in those who don't regularly exercise [47, 48]. Moreover, testosterone treatment that raises levels to the upper-end of the range can prevent bone loss, particularly in the hip area, reducing the risk of fractures and brittle bones [47].
Higher testosterone levels in this range are also connected to better brain function, including improved memory, decision-making skills, and mental clarity. Men with testosterone levels on the higher end of the normal range tend to do better on thinking tests and are less likely to experience cognitive decline as they age [49-51].
Lastly, higher testosterone levels are associated with better metabolic health. This includes lower fasting blood sugar, "bad" cholesterol, and insulin resistance suggesting that maintaining testosterone within the upper-end of the range is be beneficial for metabolic health [52, 53].
Taken together, maintaining testosterone within our optimal range offers wide-ranging benefits, potentially improving heart health, metabolic status, body composition, brain function, and overall well-being, especially as you age.
The Key Takeaway
Testosterone levels have been declining with each passing generation, and unfortunately, our reference ranges have followed suit. At Superpower, we distinguish between levels that are merely adequate to avoid deficiency and those that are truly optimal for health and longevity.
Our treatment roadmaps and recommended ranges are built on in emerging clinical research that supports a narrower and higher optimal range than conventional standards. Current studies suggests that maintaining testosterone levels within 600-900 ng/dL for men is associated with improved cardiovascular health, better body composition, enhanced cognitive function, and reduced all-cause mortality.
