With Gray’s announcement Thursday, the District joins five states that require insurers to cover surgery and other therapies for transgender policyholders. (Cliff Owen/AP)

Health insurers doing business in the District will no longer be permitted to exclude transgender-related treatments, including gender reassignment surgery, from the policies they sell, Mayor Vincent C. Gray announced Thursday.

The order issued by city insurance regulators makes explicit that denying coverage for any medically necessary treatment “designed to alter an individual’s physical characteristics to those of the opposite sex” would violate already-existing city laws against discriminating on the basis of “gender identity or expression.” It also makes clear that gender dysphoria, formerly known as gender identity disorder, is a recognized medical condition and those diagnosed with it are “entitled to receive medically necessary benefits and services,” as defined by the World Professional Association for Transgender Health.

With the new policy, the District joins Connecticut, Vermont, California, Colorado and Oregon in explicitly requiring insurers to cover medically necessary procedures and therapies for transgender policyholders.

In a statement, Gray said the new action “places the District at the forefront of advancing the rights of transgender individuals.”

“These residents should not have to pay exorbitant out-of-pocket expenses for medically necessary treatment when those without gender dysphoria do not,” he said.

Amy Loudermilk of the Mayor’s Office of Gay, Lesbian, Bisexual and Transgender Affairs said D.C. residents have seen frequent issues getting their insurers to cover these kinds of treatments and procedures. Many of the denials involved surgeries, but others involved more basic procedures — such as breast cancer screening and gynecological exams for persons undergoing hormone therapy to transition from female to male.

“There’s not one particular insurance company that was worse than the others,” Loudermilk said. But “a significant number of people who are trying to transition have faced some obstacles. … They were getting denials at all different stages.”

The requirements apply to all health policies sold in the District, including Medicaid plans and subsidized plans offered through the city’s D.C. Health Link exchange.