Van O’Neill began testosterone therapy two decades ago after medical evaluations identified low hormone levels contributing to his chronic fatigue. While the treatment initially improved his energy and motivation, he reported experiencing increased irritability and a heightened tendency toward anger.

Now 67, Mr. O’Neill described feeling as though he had “a coiled spring” inside him, tightly wound and easily triggered. He recounted an episode during a 12-step meeting where a fellow participant lightly touched his shaved head in jest. In response, Mr. O’Neill abruptly shouted, “Don’t ever put your hands on me!” Although he did not physically retaliate, he was surprised by his forceful reaction.

Mr. O’Neill, who is also managing recovery from alcoholism, has intermittently stopped and restarted testosterone therapy as he seeks to balance its positive effects against the potential for increased aggression. He advised caution with the hormone, noting the risk that it may exacerbate irritability.

Testosterone is commonly prescribed to address low hormone levels, especially in older adults experiencing symptoms such as fatigue and decreased libido. However, medical professionals acknowledge that its use can be associated with behavioral changes, including heightened aggression in some individuals. This has prompted calls for careful monitoring when patients undergo such therapy, particularly in settings like the military where testosterone prescriptions have reportedly increased and concerns about aggressive behavior are mounting.

Mr. O’Neill’s experience highlights the complex challenge of managing testosterone treatment—where the benefits to physical and mental vitality must be weighed against possible adverse emotional and behavioral effects.