But, I suppose it is the actual biological parts that are different, which I was thinking about.

one thing i think is important to recognize is that, while gender is socially constructed, so is sex to some extent. we have a number of features we generally say are “male” or “female” characteristics, including genitalia, but keep in mind that there are around 1-2% of the population that are born intersex. the way we determine sex assigned at birth is almost always through an inspection of genitalia, but for some people that isn’t conclusive.

in a lot of places, doctors will attempt “fix” these natural variations, deciding for the child which category they belong in. there is enough variation from “male” and “female” characteristics, and enough people with traits from both categories, that the categories themselves can’t really be said to have a purely biological origin, even if statistically they are highly correlated.

Am I right in thinking the main issues is that we have created a society in which sex and gender were separated and defined so distinctly, that for transexual individuals, there just is no ‘correct’ option available to them?

that’s very much part of the problem. lots of trans people really don’t fit neatly into the boxes doctors currently expect of them, especially once they’ve gone on hormones, and sharply delineating sex categories like doctors do measurably leads to less positive health outcomes for trans people. the intersex population is also affected by this kind of marginalization.

the reality is that the health of a person has a lot more to do with their specific traits than it does with the collection of traits a sex category expects them to have, which is in reality composed of a cluster of related physical, cognitive, and social traits that can vary independently of one another, and affect our health in specific ways. assuming any of these traits are one way simply because of how somebody’s genitals are supposed to be is almost always going to be more wrong than just allowing people to describe and denote their personal experience as they see fit. checking M or F on a box is, unfortunately, not really the same as just saying you have a penis or a vagina. it implies a lot more than that, even if your personal experience does not align with that implication.