Last time I looked into it - two years and a ton of red tape and a bit depending on your age/when you started (i.e. pre-puberty, puberty, post-puberty); I do know that recently (2015), the ECCC in Collegiate Cycling has a formal policy revolving around documentation of gender dysphoria...didn't see anything specifically on HRT. At least some of it depends on who you're competing under, and if these are sanctioned events. I've seen some flyers for back-alley races, targeting women and transgender (MTF) cyclists...but this was alley-cat racing, not in any way sanctioned by a major governing body. My advice is to get your paperwork ready and have it with you at all times. A few years ago at the US Cycling-sanctioned TX State Time Trials, random drug testing was enforced, so it's not just for the Tour de France or Ironman Hawaii. An estrogen level outside of the assigned competition gender could trigger an investigation, since it has been known that - on occasion - a cis-male athlete has tried to use estrogen to mask the real anabolic performance enhancing drugs.
For the FTM athlete, I can see the argument that testosterone will be an unfair advantage for the FTM athlete if he competes in the woman's division...for the same reason that anabolic steroids are prohibited for all gender classes, in just about every competitive sports. Not only will the T aid in muscle building/strength conditioning, but esp. for multi-event sports (like a multi-stage cycling event), T is also thought to help with recovery from injury and fatigue. As an example, if two athletes are at 100% of their fitness on Day 1, (hypothetically) on Day 5, one athlete (not on exogenous T) might be at 85% of their fitness, while the other athlete (on exogenous T) will be at a slightly higher residual fitness level, because of the exogenous T, allowing him to perform just abit better than his competition. This advantage shouldn't only be viewed as an in-competition advantage, but one can also see the advantage if exogenous T is used in the months of training leading up to a targeted event...the training will be more intense while the recovery will be greater. That is why there is the ban on T for sports...and unfortunately, even at levels therapeutic for the FTM, that T level will still be higher than cis-females (if he competes in the female divisions), and even with a TUE (therapeutic exemption) and competing with the men, anyone taking exogenous T will be scrutinized and potentially banned. I don't know the whole story, but I think the use of T was one reason for Balian Buschbaum to retire from athletics, so he could pursue his FTM transition (or maybe he simply wanted to move on...not sure, but he definitely would not have been allowed to use T to medically transition while competing under the Olympic banner).
