A couple of links from the US based running discussion group, LetsRun, which also allows anonymous posting and therefore discussion of the trans issue in sport:
www.letsrun.com/forum/flat_read.php?thread=10573501
Its quite an issue in the US as different States can make different rules, so there is a lot of discussion.
One elite US former female runner, Nikki Hiltz, has just come out as transgender, although she is either male or female and not fixed. It remains unclear in which division she would seek Olympic or national selection, as all her results have been in female only races and she would be ineligible on times to compete for male elite selection (she would'nt be fast enough).
It does raise the interesting question as to whether such an athlete could legally take testosterone supplements but still race against women, as the permitted IAAF limit on testosterone is several times higher than that ever naturally recorded in any woman athlete. Such an athlete, who is gender fluid, could then identify as female on the day of the race, whilst having taken testosterone enhancing drugs in a way which would not be permitted for a female athlete and only permitted for a trans athlete.
There is no suggestion from Nikki that she might actually do this, I'm simply pontificating on the possible outcomes in the future.
runningmagazine.ca/the-scene/elite-u-s-runner-nikki-hiltz-comes-out-as-transgender/
Certainly, the case of June Eastwood and her compatriots is now a bit infamous in the US, as the children's division in their state has been dominated by former male children who win and place in most of the races for girls. June's mother is particularly pushy and protective of June's rights.
runningmagazine.ca/sections/runs-races/june-eastwood-to-become-first-transgender-woman-to-compete-in-ncaa-division-i-xc/