(CNN) -- Henry Joseph Madden was a good student and track team member in high school, but he had a secret: He sometimes wore his mother's pantyhose and underwear under his clothes.

Dr. Jennifer Madden, a family physician, began her transition to being female at age 48.

"I really wanted to be a girl so bad, and that was one way for me to satisfy those feelings," Madden said. "I always felt like someone was looking over my shoulder."

The desire to be female never went away. At age 48, Madden confessed these feelings to a doctor, and started seeing a gender therapist who suggested Madden was transgendered.

Through reconstructive surgeries, electrolysis, laser procedures and voice lessons, Henry Joseph became Jennifer Elizabeth, known as Jenny. She is a practicing family physician in Nashua, New Hampshire. Watch Jenny's story "

Chastity Bono, child of performer Cher and the late entertainer and politician Sonny Bono, announced Thursday the beginning of a transition from female to a male.

While still relatively rare -- one advocate estimates that 0.25 to 0.5 percent of the American population is transgendered -- the idea of changing gender identity has become more widespread in recent years. The term "LGBT" (Lesbian, Gay, Bisexual, Transgender) is more commonly recognized, and transgendered people have been portrayed in the 1999 film "Boys Don't Cry" as well as the 2002 book "Middlesex" by Jeffrey Eugenides.

Many people who have transitioned, including Madden, say they knew they had been born into the wrong gender from childhood. As early as age 3, Dr. Julie Praus, born male, didn't understand why her father wanted to play catch. As a boy, Praus learned how to fish and hunt, but enjoyed collecting Depression-era glassware vases. Praus, 48, a psychiatrist in Brattleboro, Vermont, started living as a woman in March 2008.

Now, provide a numbered list of answers to these questions:

1. How much of the American population is transgendered?
2. Does that include Dr. Jennifer Madden?
3. What was her birth name?
4. Did Henry want to be a girl in high school?
5. Did that keep her from being a good student and extracurricular activities?
6. How old was she when she transitioned?
7. Whose idea was it, originally?
8. What kind of doctor is Jenny?
9. Is the idea of transitioning getting more common?
10. How about the term "LGBT?"
1. 0.25 to 0.5 percent
2. yes
3. Henry Joseph Madden
4. yes
5. no
6. 48
7. her gender therapist
8. a family physician
9. yes
10. yes