As far as I know, a shemale is a woman with male genitalia and big breasts from either breast implants or hormone treatments. Hormone replacements are not very healthy, or at least I don’t think they are. However, a lot of people undergo hormone replacement therapy these days.
This is the way I understand it, too. I agree that hormone replacement therapy is not the healthiest choice, but for some who feel they need to change their bodies, it’s one of only a few answers available.