According to Young and Alexander's "The Chemistry Between Us", the transgender brain was discovered by Dick Swaab "in a structure called the bed nucleus of the stria terminalis (BNST)". (page 30) That means it was not socially constructed. It also means the heterosexual brain (including sex differences) was not socially constructed either.
I agree with you that the way people express their sexuality changes over time. We are not determined by these organized brain states. One
could view that as "social construction", but I prefer making sense out of cultural trends in terms of "social mood". Here is an article about transgender and the Brazilian market from the socionomics institute. I am not a member, so I only see the introduction to this article, but I think these people are on the right track, they do not restrict themselves to gender and they try to predict cultural trend changes:
http://www.socionomics.net/2015/04/a...ons-in-brazil/ I think social mood provides us with more constraints and opportunities than do the constraints our brains provide for gender, but gender is not one of them.
According to Young and Alexander, it took 17 years for Money's research claims about Reimer to be discredited even when there was contradictory evidence from the start. One of those bringing it to an end was Milton Diamond in 1997. Earlier I was wondering if OrphanPip's view was a minority position, however, after reading the following, I think he may be expressing a position that is more generally believed: "Even today [2012 published date of "The Chemistry Between Us"], Diamond tells us, Money has adherents in the United States as well as around the world. His views are still reflected in some university gender studies programs that use cliches like 'the social construction of gender.'" (Page 15) I think the point of Young and Alexander is that the people holding back this science are liberals believing in social construction.