Can testosterone make someone gay?

Testosterone: the underrated hormone

Johnny is a masculine guy, muscular and with an angular face, who has been involved in many a brawl. One night he beats up the physically inferior Richard in front of the Prater Dome club in Vienna. What exactly the argument was about cannot be clarified later, as well as the question of which of the two was violent first. But the verdict of all of Johnny's friends is unanimous: Your buddy is "testosterone-controlled". That is why he is often aggressive and reacts uncontrollably when provoked.

  1. Testosterone is the most important male sex hormone. In animal studies, increased testosterone levels are associated with aggressive behavior towards rivals and sexual partners.

  2. However, it has not been proven that the messenger substance causally promotes aggression. Experimental studies even suggest that the hormone can promote cooperative behavior.

  3. It remains unclear what role the female sex hormone estradiol plays in the brain. It is formed in the male body from testosterone and is also likely to influence behavior.

The masculinity hormone testosterone traditionally has a bad reputation. According to the cliché, it not only ensures more pronounced masculine traits physically, but also promotes anti-social, aggressive behavior and sex addiction. The American actor Alan Alda even jokingly spoke in the 1970s of "testosterone poisoning" from which almost all men suffered and which made them behave so strangely. Even today, the term "testosterone poisoning" describes unreasonable, stereotypically negative behavior on the part of men. Whether the messenger substance actually influences social behavior has only recently been scientifically investigated - with sometimes surprising results.

Testosterone is one of the most important sex hormones and has a variety of effects in the body. It is found in the blood of both men and women, with the concentration about ten times higher in men. With them, most of the messenger substance is produced in the testes, in the so-called Leydig cells. In the female body, about half of testosterone comes from the ovaries and placenta, the other half from a precursor hormone that is formed in the adrenal cortex. Testosterone can cross the blood-brain barrier without difficulty. Therefore, its concentration in the bloodstream also determines how much of it is available in the brain - where the messenger substance affects our behavior.

In studies on animals, researchers have so far been able to confirm some prejudices about the hormone. More testosterone in the blood seems to promote physical aggression, especially in connection with territorial disputes, rank fights and sexuality. Hamsters, for example, are more willing to attack a strange conspecific if they are placed in their cage when their testosterone levels are elevated. In contrast, the hormone seems to play a subordinate role in forms of aggression without a social context, such as hunting. But does testosterone have a comparable effect on humans? This question has sparked many heated debates.

On the one hand, studies with male prison inmates, for example, have shown that the amount of the hormone in the bloodstream is related to the severity of the crimes committed. Those convicted of rape, murder or armed robbery show, on average, higher testosterone levels than someone incarcerated for theft or drug abuse. An evaluation of the disciplinary reports also showed that inmates with high levels of testosterone in their blood were more often involved in conflicts with fellow inmates. Interestingly, these findings also apply to female inmates. In a study with stock exchange traders, researchers also found a connection between the hormone concentration in the body and financial success: testosterone bolides achieve greater profits on the floor.

However, these results do not yet mean that the messenger substance is causally responsible for the behavior observed. On the one hand, only the concentration in the bloodstream was determined in these studies. However, since the brain also produces testosterone itself, the amount circulating in the blood is not directly related to the amount in the brain. On the other hand, the testosterone level in the blood changes in response to certain situations. This was shown, for example, by a study by Justin Carré of the Canadian Nipissing University: When male hockey players watched a video that showed their team's victory, the testosterone concentration in their saliva rose by around a third. If you saw a video with neutral content, the hormone balance did not change. If researchers only measure the amount of the messenger substance, the question of causality has not been clarified: Higher testosterone levels can definitely be the result of aggression instead of the other way around.