I've tried reading the other threads, but I'm having trouble teasing out a detail that may be relevant to this topic: Do we know how much of "male fertility" (particularly long term) is affected by the presence of E, and how much is changed by a lack of T? My understanding is that an anti-androgen treatment by itself would (not surprisingly) kill off T, with little effect on E, and estrogen treatment by itself would reduce T (although not as much as when combined with an anti-androgen) and E would (not surprisingly) increase (but not as much as if combined with an anti-androgen). If sterility is tied more to having high E, then this would point towards a hormone-based feminization to achieve certain effects** as inherently risky, although reducing masculinity (where T hasn't already rendered it irreversible) remains an option. On the other hand, if sterility is tied more to low T, then (aside from side effect concerns) one *might* be able to maintain a sufficient level of T while elevating E by putting together a doctor-prescribed (and monitored) cocktail of testosterone and estrogen treatment (obviously with more emphasis on the estrogen). Of course there can be side effects with being loaded with that much in hormones (if the body even permits it rather than gobbling up extra hormones until the body is down to a "normal" level), and it is even more vital than with typical HRT to have a doctor keeping an eye on things. And again, this all assumes that low T rather than high E is the problem.
It may be the case that E (being high) and T (being low) are each highly influential concerning "male" sterility. Or that we don't know, because professionals haven't studied their relative effect on fertility sufficiently, owing in good part to society's (and often medicine's) insistence on the gender binary, and also due to a small number of patients willing to put their fertility on the line. Yet it is valuable to people whose identity does not neatly fit into that gender binary (and want their body to match better) and who still want to protect their sexuality options, and sometimes they benefit from some calculations concerning risk and relative risk that are more precise than "anything could happen."
** If someone just wants cleavage, then implants would be sufficient. The premise here is that people are interested in other effects.
