You haven't compared like with like. The cases you referred to are recognised illnesses, like psychosomatism or hypochrondria.

Gender dysphoria is a syndrome of symptoms (like anxiety and depression) associated with the perception of a mismatch between a person's biological sex and their culturally determined gender identity; in other words, with a gender mismatch. The latter is NOT an illness.

The perception of such a mismatch may be more an ontological issue, regardless of whether this conflicts with Catholic moral teaching based on Natural Law theory.

People sometimes confuse gender dysphoria with the perception of gender mismatch and, wrongly, classify the entire phenomenon as illness or disorder.