Cassidy Medicine Horse was born a boy, but from a young age knew inside that she was really a girl.

Growing up, she was subjected to testosterone shots and growth hormones as her family attempted to change her. For decades, she kept her feminine feelings secret to avoid her father’s terrifying discipline, to land a job and marry, to avoid getting beaten.

“You hide any expression of femininity, you put it deep, deep, deep in the closet,” she said, “because that will get you killed.”

Deeply unhappy, Medicine Horse started seeing a psychologist. A few years ago she “transitioned” — started expressing outwardly in dress and mannerisms the woman she felt she was inside. She also started taking prescription female hormones.

“I was born a woman with a birth defect,” Medicine Horse said, “that happens to be male genitalia.”

Medicine Horse, 64, spoke last week in an interview at Montana State University, where she has earned a master’s degree in Native American studies and now is a Ph.D. graduate student in American studies.

She is starting a transgender support group, called TransMSU.

“We don’t have a choice of who we are,” she said. “We are born this way.”

Life presents many problems for a transgender woman. Medicine Horse uses the women’s restrooms at MSU and occasionally another woman is momentarily taken aback. Campus police have told her that as long as her driver’s license and passport list her as female, using the women’s restrooms is fine.

She is 6-foot-4, wears her blond hair long, and speaks softly in a low voice. Her looks reflect her heritage – half Danish, half Nez Perce (or Nimiipuu).

She calls herself both transgender – a large umbrella term for someone who feels they are the gender opposite from their biology – and transsexual – someone actively taking steps to change their sex, through hormones or surgery. For people who assume sex and gender are the same, she explained, “Sex is between your legs, gender is between your ears.”

Professors and most MSU students have been “wonderful,” she said, “totally and completely accepting.”

Yet in the summer of 2011, she was working out at the student gym one day and got sweaty.

“It struck me – Where do I shower?” she said. MSU has no private showers, something she hopes to change. It’s a human rights issue, she said.

In October 2011, Medicine Horse approached the Associated Students of MSU Senate. Though students seemed sympathetic, months went by and nothing happened.

Disappointed, she wrote to the new dean of students, Matt Caires, who took her complaint back to the Senate. She received support from the new ASMSU President Kiah Abbey and student Sen. Troy Duker.

The ASMSU Senate passed a resolution 13-0 on Sept. 6, urging the Board of Regents to add “gender identity and sexual orientation or preference” to its anti-discrimination policy, Duker said. The University of Montana student Senate also is expected to vote on the issue.

“This is about safety” and making students feel welcome, Abbey said.

Regents policy now bans discrimination on the basis of “race, color, religion, creed, political ideas, sex, age, marital status, physical or mental disability, national origin or ancestry.” It does not protect gays, lesbians, bisexuals or transgender people.

Kevin McRae, associate commissioner, said MSU and UM both ban discrimination based on “sexual orientation or preference,” to protect gays and lesbians. It is probably time to update the regents’ policy, McRae said. He added the regents would welcome any student resolutions “to ensure the dignity and peaceful and decent opportunity” for people to get an education.

Medicine Horse said when she reached puberty in the early 1960s, transgender people were arrested, fired, publicly humiliated, and subjected to electroshock treatment, scientific experiments and lobotomies.

A 2011 UCLA study estimated there are nearly 700,000 transgender individuals in this country; Medicine Horse thinks the number is in the millions. Today, many have successful careers as doctors, lawyers and scientists, she said, yet a large number commit suicide.

Medicine Horse said today she feels “tremendous.”

“I feel complete. I’m actually happy for the first time in my life. I know who I am now,” she said.

“My only regret about transitioning is that I didn’t do it 40 years ago. Maybe 50 years.”

Gail Schontzler can be reached at gails@dailychronicle.com or 582-2633.