Gender transitioning, involving behavioral, hormonal, or surgical treatments, or a combination of these, is coming to be broadly accepted as a form of “therapy.” The concept of gender transitioning, however, stands in radical opposition to a proper understanding of the nature of the human person. It presupposes that there is a “self” that is separate from the body, which happens to find itself in a body and which might therefore be in the wrong body. Yet the human person is a full body–soul unity, not a “ghost in the machine” or a spirit inhabiting the body. A particular person does not merely have a body: he or she is that body. In the words of Pope St. John Paul II, the “human body expresses the person.”
In short, a person’s sex is manifested by the body in accordance with how the person has been created, and so it cannot be in conflict with any truer or deeper sexual identity contrary to that bodily sex. This is a foundational anthropological point that no medical association or political ideology can overturn. The psychological experience of a disconnect with one’s bodily sex is not to be minimized; it calls for appropriate psychotherapy, but it can in no way be reflective of an “incorrect” sex.
Given this understanding of what it means to be a human person, a body–soul unity whose innate sexual identity is reflected in the person’s biology, it should be clear that no surgical, hormonal, or other intervention directed toward the body is capable of altering that innate sexual identity. Taking up or engaging in behavioral changes, including mannerisms, social cues, clothing, or modes of speaking that social mores ascribe to the opposite sex, does not alter the innate sexual identity of the embodied spirit, which is the human person. Hormonal interventions to block the body’s sex-specific hormones or provide the sex-specific hormones of the opposite sex likewise alter nothing of a person’s innate sexual identity. The use of puberty- blocking hormones in children with gender dysphoria is particularly dangerous, since this intervention radically disrupts the normal sequence of physical and psychological development that occurs during adolescence. One cannot simply “reverse” what has been done if the individual should change his or her mind. — from A Brief Statement on Transgenderism