edit: I meant to say "discontinued in Germany" in the title, of course. Sorry for that mistake!
I'm not sure whether I have phrased my question correctly, it is not a direct citation, rather just a rough outline from my memory.
This is a topic that interests me a lot, as a Czech and a gay guy.
I tried looking it up on google (in Czech and English), but I didn't find much concerning sexual sciences in the pre-WW2 period. Most of the works I found were about sexology during Socialism. A lot of them mentioned the prewar period, but very briefly, mostly they just compared the prewar sexology, which according to them was mainly researching "sexual aberrations", to the sexology of socialism, which focused on gender theory, scientifical emancipation, etc.
Thank you a lot for your potential answers!
I think they are referring to Hirschfeld's World League for Sexual Reform. The Czechoslovak branch, Československá Liga pro sexuální reformu, continued to exist after the German one was shut down in 1933. Czechoslovakia was sort of a hub of the interwar sexual reform movement -- the Fifth Congress of the World League for Sexual Reform (in 1932) was held in Brno, for example.
There were also a number of "sexual reform" publications in the 1930s that you can look at here. While gay sex was still criminalized during the First Republic, there was a small but growing movement to abolish those laws and recognize homosexuality as a normal part of human experience. You might be interested in reading the book Od žaláře k oltáři by Jan Seidl or checking out his thesis (in Czech).
Re. Germany, u/commiespaceinvader and u/kieslowskifan discuss a bit about that research here and link to another earlier answer about the destruction of papers by Nazis.