Why is menstruation a psychological trauma to those transsexuals?

Transexuals: Someone born with the body of a woman, but who perceives herself as male, may experience any reminders of her female biological gender -- such as menstruation -- as traumatic. It is a very painful thing to feel you are "stuck" in the wrong gendered body.

Try to Empathize?: How do you think most men would feel if they suddenly grew breasts? Began menstruating? Started being called"ma'am"? Transmen fully experience themselves as male psychologically & emotionally. So naturally menstruation is distressing, if not traumatizing, to most. Our bodies, genitals, clothes, genes don't necessarily MAP on to our gender self-identification & our gender expression.