Figure 7.

Cartoon illustrating the idea that the main difference between the various gender forms resides in the C^a2+-homeostasis system, in particular that present in some brain areas. Given that the human brain contains about 100 billion nerve cells, it is de facto impossible that two individuals have exactly the same Ca²⁺-homeostasis system in the totality of their brain, even if these two individuals are identical twins. This figure illustrates the commonly observed situation that the sexual thinking and behaviour of transgenders reflects more the situation of the other heterosexual somatic sex than their own somatic genetic sex. Between these two depicted extremes, numerous intermediate forms are theoretically possible. Indeed, it is more likely that not the whole brain but specific brain regions can display (subtle) changes in Ca²⁺ homeostasis with effects on behaviour as a result.