This policy adopted by the American Medical Association (AMA) in 2008 is based on its long-standing policies against discrimination in health care against transgender patients: the policy supports public and private health insurance coverage for treatment of gender identity disorder and opposes categorical exclusions of coverage for treatment of gender identity disorder when prescribed by a physician.
Gay & Lesbian Advocates & Defenders has published a useful fact sheet that explains the AMA resolution.
Ignatius Bau 