Some pre-op MtF transsexuals have the testes removed (called “orchiectomy”) in order to reduce the amount of hormones they need to take and increase the relative effectiveness of said hormones. Done in a doctors office with proper procedures, removal of the testes is actually a fairly minor and inexpensive procedure, although it is irreversible. I have heard that some MtF’s remain at that level of sexual reassignment, never going any further. It has its pluses and minuses.
If you want to see a (WARNING! VERY GRAPHIC LINK! DO NOT OPEN AT WORK! WELL, OK, IF YOU WORK AT AN ABBATOIR OR A HOSPITAL, THEN MAYBE. THERE’S ALSO PICTURES OF A PENIS TOO, SO IF YOU DON’T WANT TO SEE THAT DON’T CLICK IT EITHER. DON’T SAY I DIDN’T WARN YOU - AND NO, IT’S NOT PORNOGRAPHIC) narrative and pictures of a medical orchiectomy, you can click this link: http://www.annelawrence.com/kohlrustorchiectomy.html
There is reportedly a guy in Wisconsin (?) who will take yours off for $500, provided you let him eat them after he’s done.
Some doctors recommend orchiectomies in male-to-female transsexuals who are not able to afford reassignment, to reduce the risk of testicular cancer, especially in patients who are taking antiandrogens. The main disadvantage to doing an orchi is that post-surgery the remaining genitals shrink further, which reduces the skin available for the vaginoplasty later on and increases the likelihood of needing a graft for satisfactory results, with the complications that go along with grafting.
The vast majority of men seeking under-the-counter orchies, though, are people into nullification, extreme body modification, or other “extreme” sexual fetishes that have nothing to do with gender identity disorders.
This is not the case in my professional experience. But I don’t work with people whose fetishes run in this direction. Still, it contradicts what I see at work.