In females, testosterone contributes to libido, bone strength, and overall well-being, albeit in smaller quantities. In males, it drives the development of secondary sexual characteristics during puberty, such as deepening of the voice, growth of facial and body hair, and increased muscle mass. To view the amygdala, for example, as a single structure while not regarding the different functions of its sub regions would be to miss the nuanced effects seen in affective, reactive behaviors (Swanson and Petrovich 1998; Terburg and van Honk 2013). In summary, the amygdala and hippocampus are regions which are significantly pinpointed in many testosterone studies. Witte et al. (2010) studied 34 healthy male and female participants and found an inverse correlation between testosterone levels and the opercular left inferior frontal gyrus, with testosterone explaining 2.2 % of the variance. A systematic review of the literature of structural MRI in relation to testosterone levels may shed light on neurodevelopmental effects of the hormone. However, a growing number of neuroimaging and single-dose administration studies suggest that testosterone has a more nuanced role in social and emotional behaviors, and especially promotes dominance behavior (Eisenegger et al. 2010; van Honk et al. 2012). In the studies considering endogenous levels of testosterone, stimuli-invoked activations relating to testosterone levels were noted in the bilateral amygdala/parahippocampal regions and the brainstem. Furthermore, we conducted a review of structural MRI i.e. voxel based morphometry (VBM) studies which considered brain volume in relation to testosterone levels in adults and in children. We conducted a meta-analysis of functional magnetic resonance imaging (fMRI) studies of testosterone administration, and of fMRI studies that measured endogenous levels of the hormone, in relation to social and affective stimuli. Thyroid hormones, which regulate metabolism, also influence mental health, with imbalances leading to mood disorders. have been undertaken on the relationship between more general aggressive behavior, and feelings, and testosterone. Higher testosterone levels in men reduce the risk of becoming or staying unemployed. If a father's testosterone levels decrease in response to hearing their baby cry, it is an indication of empathizing with the baby. For instance, fluctuation in testosterone levels when a child is in distress has been found to be indicative of fathering styles. While the extent of paternal care varies between cultures, higher investment in direct child care has been seen to be correlated with lower average testosterone levels as well as temporary fluctuations. Fatherhood decreases testosterone levels in men, suggesting that the emotions and behaviour tied to paternal care decrease testosterone levels.|Competitiveness is yet another area where testosterone leaves its mark. Assertiveness is another trait often linked to testosterone. It’s like the body’s own love potion, influencing everything from arousal to sexual satisfaction. Instead, it might manifest as a subtle confidence in social situations or a drive to excel in one’s chosen field. Speaking of aggression, let’s address the elephant in the room. Testosterone acts like a chemical mood ring, influencing our emotional state and stability.|As men age, their testosterone levels naturally decline, a process known as andropause. The role of testosterone in cognitive decline and aging is an area of growing research interest. This effect may be related to testosterone’s influence on the brain’s reward system, potentially increasing the appeal of high-risk, high-reward situations. One of the most well-documented cognitive effects of testosterone is its impact on spatial abilities. Factors such as age, sex, overall health, and environmental influences can all impact how testosterone affects a person’s emotional state.|Additionally, further exploration of the nuanced relationships between testosterone and specific psychological outcomes, such as social cognition and prosocial behaviors, will enrich our understanding of the hormone’s broader influence. Saad has researched how hormones affect and are affected by consumer behavior, such as how conspicuous consumption affects testosterone levels, how testosterone levels affect risk-taking, and how hormones in the menstrual cycle affect buying decisions. The behavioral effects of testosterone are modulated by a complex interplay of factors, including other hormones, neurotransmitters, genetic predispositions, and environmental influences. It’s worth noting that the cognitive effects of testosterone can interact with other factors, such as stress levels, overall health, and environmental influences.} Research suggests that certain nutrients can boost testosterone. A testosterone deficiency is characterized as less than 300 nanograms per deciliter of testosterone in the blood. Men with low testosterone can have a low sex drive or erectile dysfunction, and they may experience hair loss, reduced muscle mass, exhaustion, irritability, or depression. This viewpoint sees traits as having the same psychological meaning in everyone. It tends to use case studies for information gathering. "Personality is the dynamic organization within the individual of those psychophysical systems that determine his characteristics behavior and thought" (Allport, 1961, p. 28). Moreover, the relationship between testosterone and aggression can be bidirectional. Cultural and environmental factors play a significant role in shaping how testosterone-related aggression is expressed. This effect isn’t limited to physical competitions; it’s also observed in cognitive contests and social competitions for status or resources. This rise in testosterone can then lead to increased aggressive behavior, but only if the social context demands it. While testosterone can certainly promote aggression, it’s not a simple cause-and-effect scenario. Our main findings were that activity and structure of the parahippocampal/amygdala region were related to differing levels of both endogenous and exogenous testosterone. However, in girls a different pattern emerged in that testosterone is linked to reduced brain volume in many of these regions. 119 individual 9 year old twins were tested, and it was found that those with a male co-twin had larger total brain and cerebellum volume than those with a female twin. Bramen et al. (2012) studied 130 healthy adolescents and reported that testosterone positively correlated with age in boys, but not girls. Conversely, when levels of midlife testosterone in men are correlated with regional density in later life, larger gray matter volumes in frontal and parietal regions, and smaller occipital volumes are seen. Specifically, activations related to endogenous levels of testosterone were in the right cornu ammonis (CA) hippocampus, and the left basolateral amygdala (BLA). Perhaps one of the most widely recognized behavioral effects of testosterone is its influence on aggression. One of the primary ways testosterone influences behavior is through its effects on brain structure and function. Testosterone also appears to relate to brain structural development, but the VBM studies that we reviewed here show modulatory effects by gender, age, and other circulating hormones, and so more research is needed to clarify this area. Two studies measured testosterone levels before birth, and linked these to brain volumes in childhood. A hidden puppet master, testosterone pulls the strings of human behavior, choreographing a complex dance of aggression, desire, and cognition. The range of conditions and findings in this review make it clear that, when assessing the effects of testosterone on neural activity, structure and behavior, many variables need to be considered in order to appreciate the subtleties of the effects. There is disagreement about the clear distinction of a dominance or social aggression network in these frontal-limbic-brainstem regions (Panksepp and Biven 2012). We conducted an ALE meta-analysis to examine fMRI results related to both exogenous and endogenous levels of testosterone in healthy populations. It is unclear if the use of testosterone for low levels due to aging is beneficial or harmful. Attention, memory, and spatial ability are key cognitive functions affected by testosterone in humans. Conflicting results have been obtained concerning the importance of testosterone in maintaining cardiovascular health.
