Gender-affirming hormone therapy, including estrogen and androgen-blockers (also known as “T-blockers”), is likely to impair or even halt sperm production.
The effect seems to be dose-dependent. In one study, researchers found that low-dose estrogen therapy had no impact on sperm concentration or motility, while a higher-dose regimen resulted in reduced sperm motility after just a few days and reduced sperm concentration after 2 weeks.