Close your eyes and think about testosterone. Did body hair, a muscular frame or masculinity, come to mind? Highly likely. That is because, even though both men and women have this hormone, it is what distinguishes men from women. What is lesser known, however, is testosterone’s role in how the brain develops in the womb and its influence on health and behaviour throughout adulthood.
How testosterone shapes the brain
Testosterone’s role begins in the womb, shaping more than the physical appearance that distinguishes males from females. Dr Peter Celec, a medical researcher at the Institute of Molecular Biomedicine – Faculty of Medicine, Bratislava, Slovakia, says, “The general consensus is that this (brain changes) happens during prenatal or neonatal development of the brain.”
During adolescence, testosterone shapes social and emotional behavioural development. A hypothesis suggests that the brain size of certain regions is related to testosterone. A visible increase in grey matter improves connectivity across the brain, with heightened activity of regions like the amygdala, hippocampus, hypothalamus, and pituitary gland. This is probably why adolescent boys struggle with their thoughts and feelings as testosterone production suddenly surges.
Dr Vishnu Vasudevan, an endocrinologist from Moulana Hospital, Kerala, says that the effect of testosterone is not limited to any region specifically. However, it is known to exert some influence on the prefrontal cortex of the brain along with its cross-talk with the amygdala, the emotional centre of the brain, he adds.
As a type of androgen hormone, testosterone binds to androgen receptors in the brain, activating signals that delay nerve cell death and anti-inflammatory pathways and contribute to cognition. These androgen receptors are activated by testosterone and other variations of testosterone in the body, like estradiol and dihydrotestosterone, says Dr Celec.
Cognitive effect of testosterone
Sex hormones are known to change mood and behaviour, but scientists agree that testosterone in men has been linked with better spatial abilities than women.
However, while the social and political structure is primarily dominated by male leaders as decision-makers, a study shows otherwise. Topically applied high testosterone levels (through hormone creams) have been associated with impulsive decision-making. In an experiment to see how testosterone affects decision-making, men on testosterone supplements made quicker and more impulsive decisions compared to men who were not on supplements.
If you walk through the parks of cities during mid-day, you might sometimes catch a bunch of retired men who walk and chat together. This could be linked to research showing that testosterone levels in older men were an indicator of social cognition in old age.
Emotional effect of testosterone
Teenage boys have a reputation for being highly emotional and impulsive. Yet, a recent study showed that compared to adult men, boys with higher levels of testosterone had better emotional regulation. It indicates that higher testosterone could mean better expression and management of emotions.
For years, people associated the male hormone with male aggression. However, the scientific consensus shifted in 1991, showing no real link between testosterone and aggression. Instead, it became an indicator of greater social dominance and reduced aggression.
Dr Celec says there is no clear indicator of what level of testosterone results in mood changes. It varies from person to person. The higher activation of androgen receptors in the brain has different effects on the aggression pathway.
“But again, the view that testosterone is responsible for amygdala-mediated aggression is far too simplified,” clarifies Dr Celec.
Effect of testosterone imbalance
One aspect of an imbalance in testosterone that is often ignored is depression and anxiety. Low testosterone levels have been linked to depression and anxiety in men. Dr Vasudevan shares the story of a 30-year-old man from Palakkad who suffered a snake bite as a child. The venom of the bite affected his pituitary gland, which regulates testosterone secretion in the body, thus lowering his testosterone levels,
On beginning testosterone supplementation, he noticed that the young man’s mood improved drastically. Slowly levelling up his testosterone dose under Dr Vasudevan’s care showed a visible improvement in the young man’s well-being. Along with other physiological changes, his mood improved, and he was better equipped to handle any disruptions in his daily life.
“Testosterone itself and alone is, however, nearly helpless,” says Dr Celec on whether testosterone supplementation can change brain wiring permanently.
Understanding how testosterone influences mood, behaviour and depression still requires further investigation. It is clear that it plays an important role in cognition, behaviour and emotional regulation. Its effects are not strictly binary and go beyond gender-related sexuality and aggression.