I have been looking back at all the (considerable) information I have collated over past four months or so, and I was trying to find the IOC regulations regarding transgender women and when the decision was made to allow them to compete in women's sport.
The meeting happened in Lausanne in November 2015, and as far as I can tell, most of the World's individual sporting organisations will be bound by these rules.
stillmed.olympic.org/Documents/Commissions_PDFfiles/Medical_commission/2015-11_ioc_consensus_meeting_on_sex_reassignment_and_hyperandrogenism-en.pdf
2.Those who transition from male to female are eligible to compete in the female category under the following conditions:2.1.The athlete has declared that her gender identity is female. The declaration cannot be changed, for sporting purposes, for a minimum of four years.2.2.The athlete must demonstrate that her total testosterone level in serum has been below 10 nmol/L for at least 12 months prior to her first competition (with the requirement for any longer period to be based on a confidential case-by-case evaluation, considering whether or not 12 months is a sufficient length of time to minimize any advantage in women’s competition).
www.theguardian.com/sport/2016/jan/25/ioc-rules-transgender-athletes-can-take-part-in-olympics-without-surgery
Former IOC medical commission chairman Arne Ljungqvist who was present at the meeting, said the consensus was driven by social and political changes.
So, forget the biology and physiology, simply let the touchy feely stuff rule.