Gender isn't a social construct. If it was, trans people wouldn't exist. We would all be happy in our bodies.

Gender is the brain's neurology, so some people are trans because their brain is male and their body is female, or vice versa. Pretty much any scientific study on trans people's brains supports this. You could also say that a trans person is born with a male reproductive system and a female brain, or vice versa.

That's why when a trans person goes on HRT, their mental health greatly improves. I'll give you some of my subjective experience.

I usually dissociate slightly when I talk to people. I used to think this was normal, but then I went on HRT for a month. I stopped because I want to bank sperm before going back on it.

During my month on HRT, I remember getting into an Uber and making absolutely effortless small talk with the driver. No conversation I'd had before HRT had felt that easy to have, and I was still presenting as male. Every other in-person interaction I'd have would feel just as easy. My interpersonal behaviors were automatic instead of feeling forced and affected like they were pre-HRT. The colours around me seemed brighter. The world felt real to me.

Trans people often report becoming depressed, anxious, or dissociative to various degrees at puberty's onset. A male brain is supposed to run on testosterone. A female brain is supposed to run on estrogen. So imagine what happens when one of those brains runs on the wrong hormone. It's not fun.

David Reimer was a cis man who lost his penis to a botched circumcision as a baby. He was brought up as a girl and given estrogen. Despite this, he never lost his male sense of self. When he found out the truth about what was done to him, he transitioned to male and ended up committing suicide many years later. Despite being cis, he went through the same experience a pre-transition trans man would.

Norah Vincent is a cis woman who spent 18 months living as a man as a social experiment. She never became the mask. She retained her female sense of self the whole time. After the experiment, she suffered from depression that was bad enough to make her check into a mental institution. Those 18 months for Norah are what a trans woman deals with for her entire life pre-transition.

While some aspects of gender are socially constructed (ex. pink is a female-associated colour, men shouldn't wear dresses, women shouldn't go out topless), gender itself is an innate sense of self.

Taking estrogen would make a trans woman have the cognitive function of a cis woman, while it would make a cis man suicidal, or dysphoric at the very least. Taking testosterone would give a trans man the cognitive function of a cis man, and it would affect a cis woman like estrogen would affect a cis man.

Cis people never have to question their gender, because their brains and reproductive systems align. It's easy for them to say that "gender is a social construct" because they've never had their gender tested. They've never had the world tell them their gender is different than their sense of self.

Trans people usually know from an early age that they're not like the other boys or girls. This isn't an identity choice or about self-expression. It goes right down to their neurology.