entropy As others have said, this is false. You don't require a referral from an endo to get a GD letter from a psych.
That said, IDK if any psych will really be willing to issue a GD letter to a teen. Most endos will also refuse to treat. It's the sad reality.
Heck, I was asked today about parental acceptance as a 30+ year old. The degree of infantilization that Indian psychs have for trans people is absolutely wild.