How does Testosterone Influence Brain Function and Mood Regulation?

The intriguing history of testosterone is indeed diverse, and it’s inextricably linked to the understanding of male virility and the function of testicles.

For thousands of years, farm owners have recognized that castrating domesticated animals makes them infertile and more docile and largely diminishes their sexual abilities.

However, it was not known until the 1930s that what these animals were losing was a specific substance now known as testosterone.

Testosterone plays a key role in developing male sexual organs even before birth. During puberty, it becomes a crucial hormone responsible for initiating the development of secondary sexual characteristics such as body hair growth and deepening of voice. Furthermore, testosterone:

  • It is associated with aggressive and dominant behaviors in men.
  • Binds to neurotransmitters to stimulate muscle growth and protein synthesis.
  • Enhances and maintains high bone density when levels are elevated.
  • Aids men in burning fat more efficiently than women.
  • Supports the production of red blood cells, which is beneficial for heart health.
  • Influences cognitive functions and thought processes in the brain.

The diversity and range of scientific research on testosterone and its effects on different body parts are vast.

Today, testosterone plays an imperative role in embryonic development, brain function, sexual behavior, muscles, bones, and emotional states.

Produced by Leydig cells in the testicles, most testosterone is secreted into the bloodstream, from where it can travel as far as the brain. Some testosterone remains within the testes, establishing an environment conducive to producing mature sperm.

1. The Influential Role of Testosterone on Brain Function

It is well established through numerous studies that testosterone receptors exist in our brains, impacting our cognitive processes and behavioral patterns. Many of these effects pertain to sexual behavior, particularly in males. There’s an increasing body of evidence suggesting that testosterone influences certain aspects of cognition and moods – an indispensable facet of brain function.

Men with optimal testosterone levels often exhibit improvements in cognitive ability and memory. In contrast, testosterone deficiency can lead to physical weakness and lethargy, negatively impacting their daily activities and academic performance. Such deficiencies can also severely impact self-esteem, especially during adolescence.

Investigations into the effects of testosterone, such as a notable study conducted by Harvard on lizard sexual behavior, reveal that testosterone directly influences the brain. Typically, when a male and a female lizard are enclosed together, they display specific behaviors that signal interest and result in mating. The male exhibits brightly colored skin on the underside of their neck, known as the dewlap, and performs repetitive pushing movements. The female reciprocates with similar, though less intense, movements. Eventually, the male grabs the female’s neck with his mouth, and mating ensues.

However, castrated male lizards, when introduced to a female, behave as if indifferent to her presence: they do not extend their dewlaps, don’t engage in repetitive movements, and certainly do not mate.

Intriguingly, when a minute amount of testosterone was introduced into a specific part of the castrated male lizard’s brain responsible for sexual behaviors, it resumed all normal behaviors despite undetectable testosterone levels in its bloodstream. This strong evidence affirms that testosterone directly affects brain function.

Modern research has discovered that testosterone may improve spatial memory and overall quality of life in male patients with Alzheimer’s Disease. Evidence suggests that testosterone has neuroprotective effects in older men, though an optimal level may exist, beyond which it could have detrimental consequences.

As for the underlying mechanism, the neuroprotective effects of testosterone may be attributed to its conversion into estrogen within the brain; alternatively, it could be due to testosterone directly binding to regions with a high density of androgen receptors, such as the hippocampus (crucial for memory formation).

2. The Role of Testosterone in Mood Regulation

Sex hormones, including testosterone and estrogen, have been clearly shown to influence cognitive functions and social and emotional responses.

Consider, for instance, that women tend to be more proficient at expressing emotions and recognizing facial expressions, while men exhibit different emotional expression and recognition patterns. This can largely be attributed to the dominant sex hormones in each gender – estrogen in women and testosterone in men.

Higher testosterone levels can be associated with decreased empathy and heightened aggression, negatively impacting socioemotional functioning.

Interestingly, while low sexual function and associated depression is more prevalent in men, women with inherently lower testosterone levels are more sensitive to its fluctuations.

Research has demonstrated that testosterone amplifies an individual’s response to anger while diminishing their response to fear. Compared to individuals with low testosterone, those with higher levels presented a longer gaze upon angry faces and a more fleeting interaction with fearful ones.

One drug manipulation study discovered that testosterone heightened women’s heart rates when they viewed angry faces. Yet, it detrimentally impacted their ability to identify those emotional expressions accurately.

Neuroimaging studies have found a significant correlation between men with higher testosterone levels and amplified activation of the amygdala – the brain region associated with processing negative emotions – when viewing angry faces.

Based on these findings, vanHonk and colleagues proposed that testosterone may dampen the avoidance response induced by fear-evoking stimuli (shorter gaze duration) and enhance the aggressive response triggered by anger-evoking stimuli (increased heart rate, heightened amygdala activation, reduced recognition accuracy, prolonged gaze duration), ultimately resulting in increased aggressive behavior.

To summarize, testosterone not only influences cognitive functions and has neuroprotective effects on the brain but also significantly impacts emotional expression, promoting aggressive behavior and individual reactions to angry facial expressions.

3. Three Demographics that May Exhibit Low Testosterone Levels

Individuals Aged Over Forty

Testosterone production is closely tied to age; as individuals age, their bodies typically secrete less of this crucial hormone. Particularly for men past forty, testosterone levels tend to decline yearly at approximately 1.6%. By the time they reach their fifties or sixties, their testosterone concentration can be markedly lower than that of their younger counterparts.

This testosterone decline may contribute to age-related symptoms, including weight gain, insomnia, and increased perspiration during physical activity. Moreover, many men also report a noticeable decrease in sexual function post the age of forty.

Overweight Individuals

Obesity can often correlate with low testosterone, a scenario frequently called metabolic syndrome. Chronic health conditions precipitated by obesity, such as hypertension, hyperlipidemia, and hyperglycemia, can suppress the body’s testosterone production. Consequently, to avoid hindering the evolution of secondary sexual characteristics, overweight individuals must prioritize weight loss.

While aging naturally reduces testosterone synthesis, lifestyle choices also play a crucial role. Factors such as unhealthy diet, sedentary behavior, smoking, and excessive alcohol consumption can negatively impact hormone levels.

Men with Unapparent Secondary Sexual Characteristics

Given testosterone’s significant role in human development, men deficient in this hormone tend to have less evident secondary sexual characteristics. Generally, they may exhibit less distinct masculine traits. This can be attributed to various reasons, such as the effects of certain medications or hereditary conditions. Additionally, complications with testosterone synthesis can lead to similar symptoms.

Should you or someone you know experience a noticeable regulation in testosterone levels, staying calm, respecting the individual’s privacy, and approaching the matter constructively is vital.


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