bioavailable testosterone

10 Scientifically Proven Upsides of Bioavailable Testosterone

In Free Testosterone and SHBG by MarcelLeave a Comment

Testosterone, globulin bound testosterone, free testosterone, and bioavailable testosterone – the main androgens.

Testosterone is the hormonal core of masculinity and its what makes a man a man. The benefits of testosterone are well-known and optimal testosterone is desired by every normal man. From old men needing more energy and vitality to young athletes wanting inhuman strength.

Testosterone as a total is not where most of the benefits come from though. Total testosterone is simply all the testosterone flowing in the bloodstream, both bound to binding globulins and unbound testosterone. The small and unbound fraction of testosterone called free testosterone is the bioavailable testosterone that exerts androgenic effects in the body.

Bioavailable testosterone is where the benefits of testosterone are.

10 Scientifically Proven Upsides of Bioavailable Testosterone

  1. Expression of force and power
  2. Increases dominant behavior
  3. Increases athletic performance like squats and sprints
  4. Increases physical performance
  5. Increases bone mineral density
  6. Increases IGF
  7. Increases mood
  8. Greater bone mineral density, lean body mass, and total fat mass
  9. Increases processing speed performance
  10. Increases adaptation to medium-intensive exercise

Expression of Force and Power

Bioavailable testosterone increases the expression of physical force and power.

In an experiment they had a group of elite male rugby players do jumps. The peak force and peak power was the highest in the groups with the higher free testosterone concentrations.

  • Free testosterone significantly correlated with peak rate of force development.
  • Free testosterone significantly correlated with force at 100 milliseconds.
  • Free testosterone significantly correlated with the countermovement jump.

The experiment’s conclusion is that the expression of force and power in an elite athletic group is to some extent dependent on free testosterone concentrations and existing strength.

Increases Dominant Behavior

Bioavailable testosterone increases dominant behavior.

Some notes from this study that collaborates 422 studies and experiments:

  1. Free testosterone is correlated with self-report, observational, and implicit measures of dominance motivation in healthy adult men and women.
  2. Testosterone correlates with factors of dominance behavioral system.
  3. Levels of testosterone predict dominance behavior among adolescents and and college roommates.
  4. In a prison study men with history of violent interpersonal crimes had higher basal testosterone levels than men with a history of property crimes.
  5. In the same study testosterone predicted more rule-breaking within the prison setting, especially rules involving overt confrontation.
  6. Men with low testosterone are motivated to maintain low status.
  7. Testosterone predicts range of aggressive behaviors like fighting and confrontations in prisons and and willingness to administer larger shocks to competitors in laboratory studies.
  8. Testosterone administration doesn’t consistently increase aggressive behavior and testosterone is correlated better with dominance than aggression.
  9. Testosterone is related to self-perceived power and confidence.
  10. Testosterone relates to diminished sensitivity to threat.
  11. High testosterone relates to lower interpersonal sensitivity.
  12. Testosterone correlates with antisocial behavior.
  13. Testosterone relates most strongly to the tendency to protest or disobey commands.

Increases Athletic Performance Like Squats and Sprints

Bioavailable testosterone increases athletic performance.

This experiment had 10 weight-trained athletes that were men divided into two groups – average squatters and good squatters based on their 1 repetition maximum squat.

Testosterone correlations were strong and significant in the good squatters but not significant for the average squatters.

“These results suggest that free testosterone is a strong individual predictor of squat and sprinting performance in individuals with relatively high strength levels but a poor predictor in less strong individuals.”

bioavailable testosterone

Increases Physical Performance

Bioavailable testosterone increases physical performance.

  1. An experiment done on 45 young elite soccer players found out that there was a 42.88% of variance in countermovement jumps and free testosterone concentration was the primary contributor.
  2. Another experiment found out that higher continuous free testosterone was positively associated with short physical performance battery score, usual walking speed, lower risk of developing mobility limitation, and lower risk of poor subjective health.

Increases Bone Mineral Density

Bioavailable testosterone increases bone mineral density.

1. Low testosterone causes inadequate bone development and a lower bone mineral density (study).

bioavailable testosterone

bioavailable testosterone

2. A decrease in free testosterone is partially associated with a decline in bone mineral density (study).

3. Low free testosterone is associated with low bone mineral density (study).

4. Free testosterone is associated with higher lumbar bone mass (study).

5. In the experiment here 131 men with low testosterone and history of fracture were given testosterone, calcium, and cholecalciferol. The bone mineral density increased but not by much in this experiment.

Increases IGF

Bioavailable testosterone increases IGF, one of the most anabolic hormones.

This experiment found out some interesting stuff:

  1. Administration of testosterone increases serum levels of IGF-I.
  2. There’s an inverse relation between serum IGF-I and SHBG.
  3. Serum levels of IGF-I decreases with increasing SHBG.
  4. Serum levels of IGF-I increases with free testosterone.
  5. IGFBP-1 has no correlation with SHBG.
  6. IGFBP-1 is positively correlated with total and free testosterone.

“Among healthy young and middle-aged men, there is an association between serum levels of free-testosterone and SHBG on the one hand, and serum IGF-I and IGFBP-1 on the other.”

bioavailable testosterone

bioavailable testosterone

bioavailable testosterone

There are plenty of studies and experiments confirming the positive correlation between bioavailable testosterone and IGF – study, study, study, study, study, study.

Increases Mood

Bioavailable testosterone increases mood, mental health, and overall well-being.

This experiment set out with the intention to find the association between sex hormones and depressed mood in community-dwelling older men. 856 men of ages 50-89 took part for about 3 years.

The findings of this experiment are:

  • Low bioavailable testosterone levels and high Beck Depression Inventory scores were associated with weight loss and lack of physical activity, but not with cigarette smoking or alcohol intake.
  • Beck Depression Inventory score was significantly and inversely associated with bioavailable testosterone, independent of age, weight change, and physical activity.
  • Similar associations were seen for DHT.
  • Bioavailable testosterone levels were 17% lower for the 25 men with categorically defined depression.
  • Total and bioavailable estradiol was not associated with depressed mood.

bioavailable testosterone

Greater Bone Mineral Density, Lean Body Mass, and Total Fat Mass

Bioavailable testosterone increases bone mineral density and lean body mass while decreasing fat mass.

This study says total testosterone directly associates with bone mineral density. Free testosterone is positively associated with hip bone mineral density, lean body mass, and body fat (the experiment is done on women, in men its the opposite).

bioavailable testosterone

  1. Testosterone therapy increases lean mass and decreases body fat in old men (study).
  2. Low free testosterone is associated with loss of muscle mass (study).

Increases Processing Speed Performance

Bioavailable testosterone increases processing speed performance.

This experiment found out that free testosterone levels are significantly associated with increased skew in the reaction time distribution. This association is a strong predictor of processing speed performance.

bioavailable testosterone

Increases Adaptation to Medium-Intensive Exercise

Bioavailable testosterone increases adaptation to medium-intensive exercise.

An experiment was set out for 4 weeks consisting of medium intensive exercise with 2 groups in the experiment.

One group with less than 20% work duration at the level above the 80% threshold anaerobic metabolism and the other group with more than 20% work duration at the level above 80% threshold anaerobic metabolism.

No significant differences between total testosterone, growth hormone, and cortisol before and after exercise in the groups. Free testosterone didn’t change in group 1, but it increased in group 2.

The experiment concludes that free testosterone can be used for evaluating the degree of athlete’s adaptation to medium intensive exercise.


There you have it – 10 scientifically proven upsides of bioavailable testosterone / free testosterone.


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