It is a very old fashioned notions about the endocrine system that also lead to the belief hystrionic women would benefit from a hysterectomy as it was believed that sex hormones alone effect mood.
There is still so much to be learned and unlearned about hormones and their effect on mood and behaviour.
The idea that gender and behaviour is defined either by the presence of estrogen or testosterone levels is a false and simplistic view that even many doctors still prescribe to.

NorAdrenalin, serotonin, cortisol, thyroxin, melatonin... The list is long. All of these hormones effect mood and intern can effect behaviour. They work together in a delicate balance.