Testosterone – Effects on the Brain and Behavior

2D structure of testosterone

Testosterone has more effects on the human body than merely producing secondary sexual characteristics. It has been found that testosterone has significant influence on the male brain. These effects start from a young age, perhaps as young as infancy.

The impact of testosterone on the brain may be a part of the effects this hormone has on other organs like the heart and lungs. The sexual differentiation of the male results in men having larger organs like the heart and lungs and possibly the brain as well. It was found in various studies that men have longer total length of nerve fibers than women. However, women have more synaptic connections than men. (Synapses are the junctions or communication points between one brain cell (neuron) and another). Recent studies show that gender differentiation of the brain even occurs during the fetal stage as a result of testosterone. The male brain is hence larger than the female and in keeping with the larger head and body.

Though some differences in male and female behavior may be because of testosterone, it is found that aggressive behavior cannot be fully attributed to levels of this hormone alone. In fact, the risk taking capacity of the male is only slightly enhanced by increased levels of testosterone. But memory, attention and spatial recognition abilities are clearly influenced by this hormone. This means that higher levels of testosterone increase the ability for concentration and also the ability to memorize facts. There is also some evidence that suggests some correlation between low levels of testosterone and onset of diseases such as Alzheimer’s disease. In fact, testosterone is one of the drugs used in treatment of Alzheimer’s disease and cognitive defects. An interesting observation was that both high (hyper) and low (hypo) levels of testosterone were found to be involved in these conditions. This should serve to warn those who blindly use testosterone as a sure-shot remedy (cure all) for treatment of Alzheimer’s disease. It means that, testosterone is definitely not an over-the-counter remedy that should be be used by the layman, but a drug that should be prescribed with caution by the experienced physician.

Aggression and Aggressive Behavior

Until recently it was believed that aggressive behavior was directly related to the level of testosterone in a man’s blood. Not so any more. New studies show no definitive evidence of correlation between aggression and high testosterone levels. On the contrary, lower levels of testosterone (hypo) were found to be associated with more aggressive behavior. This is indeed a new discovery and needs more analysis before firm conclusions can be derived. It must be noted that the nerves, nerve connections, synaptic activity and endocrine glands (glands that release hormones) are intricately related and form what is called the neuro-endocrine axis. This is a very complex structure of which testosterone and the male gonads (testes) are only a part. As such more study is required to accurately determine cause/effect relationships among the various systems.

For more information see: Testosterone

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