The Centers for Medicare and Medicaid Services are currently reviewing and updating their policy regarding surgical needs and coverage of transgender patients. The 30-day public comment period started yesterday. Please consider submitting your comments via the form at the review webpage.
The scientific literature is still relatively sparse (for the simple reason that the trans* population is relatively sparse), but for those who are interested and not already aware of these, here are some links to studies on the outcomes and effects of sexual reassignment surgery:
And on the note of physiology and transsexuality, there have also been many studies indicating physiological connections between binary-identified trans* people and the gender or sex with which they identify, for example: