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What is hormone therapy for transgender people? Experts explain this decades-old treatment.

Silhouette of person's head with eyes lit, against mashup image of gears, pills, vials, male and female symbols, puzzle pieces, a brain and a hypodermic needle.
Perhaps one of the most misunderstood elements of gender-affirming care is hormone therapy. (Getty Images; Illustration by Victoria Ellis for Yahoo)

In a world in which gender is becoming increasingly fluid, trans and nonbinary people are taking unprecedented control over their bodies through a variety of gender-affirming health care services. And a major, often misunderstood, offering in that toolkit is hormone therapy, which involves administering hormones — estrogen for transgender women and testosterone for transgender men — to bring about physical changes in the body that are consistent with one's gender identity.

Hormone therapy — also called gender-affirming hormone therapy (GAHT), hormone replacement therapy (HRT), transgender hormone therapy (THT), estrogen hormone therapy (ERT) or testosterone hormone therapy (TRT) when used in this context — has as of late been shrouded in controversy, especially when it comes to the therapy for young people. It's sparked impassioned protests around the ethics and practicalities of the medical intervention and led to 17 states banning gender-affirming hormones for minors who are transgender (people who feel their physical body doesn't match their gender identity) and nonbinary (who don't identify with any gender at all), as conservative lawmakers argue it may have irreversible side effects later in life — though the mental-health benefits, argue supporters, far outweigh any potential medical risks.

Adding to the discourse was an announcement made in April by YouTuber Chris Tyson, 26, a frequent collaborator with YouTube celebrity MrBeast, who has 150 million subscribers. Tyson announced in a tweet that they identify as gender nonconforming (neither male or female) and have begun taking estrogen as part of their gender transition process.

Tyson’s message prompted a wave of anti-trans backlash online so intense that MrBeast (whose real name is Jimmy Donaldson) stepped in to defend his friend in a tweet against the "transphobia." Soon after, Tyson began sharing their experience with what they called "life-saving" hormones, imploring lawmakers to "let people make informed decisions about their own bodies."

Of course, Tyson is far from the only person to use and advocate for hormone therapy. For a growing number of gender-expansive individuals, it's become a crucial part of their journey toward self-discovery. And as society grapples with changing attitudes toward gender and identity, experts say the experiences of people like Tyson offer a glimpse into a complex and evolving landscape.

Hormone therapy: What is it?

As Susan Boulware, associate professor of clinical pediatrics and medical director for Yale School of Medicine's Gender Program, tells Yahoo Life, hormone therapy is a broad term used to describe "individualized dosing of medications" that replace one's natural hormones, estrogen or testosterone, when the body doesn't make enough of it, or does not produce it at all.

Though hormone replacement therapy has been a popular form of treatment for decades, used to offset symptoms of menopause in women and andropause (aging-related hormone changes) in men, hormone therapy has also been a tool for gender transitions since the early 20th century.

In the 1930s, when scientists were first "able to synthesize the hormones in a lab," Boulware explains, physicians saw huge benefits for people experiencing severe gender dysphoria — defined by the American Psychiatric Association as the "psychological distress that results from an incongruence between one's sex assigned at birth," based on external genitalia, "and one's gender identity," meaning the psychological sense of one's gender.

"In 1939, Michael Dillon was among the first, if not the first, transgender man to request testosterone for masculinization (and later, the first trans man on record to have gender-affirming surgery)," she says. "He himself was a physician and had heard about the use of T [testosterone] to treat excessive menstrual bleeding so he asked that physician for T as gender-affirming therapy."

"As the availability of testosterone and estrogen increased, its use among trans and nonbinary folks did as well, though obviously to much less extent than in cisgender folks," Boulware says, referring to those whose biological sex is in line with their gender identity. A growing number of trans pioneers also blossomed during this time — including Dora Richter, the first known trans person to undergo gonadectomy (removal of the testes), in 1921, and vaginoplasty (creation of a vagina and vulva) in 1931; and Lili Elbe, the first known trans woman to undergo hormone therapy as part of a transition process, before beginning surgical interventions in 1930. (The 2015 film The Danish Girl, starring Eddie Redmayne, was inspired by Elbe's life.)

Black-and-white image of Lili Elbe posing next to a tree.
Lili Elbe (1886-1931) was the first known trans woman to undergo hormone therapy as part of a transition process. (Photo: ullstein bild/ullstein bild via Getty Images)

Nearly 20 years later, doctors like Harry Benjamin (the "American father of transgender health care," Boulware notes) began using hormones to treat people experiencing gender dysphoria. And throughout the rest of the 20th century, many physicians have followed his example.

Regarding the term "hormone-replacement therapy," or HRT, now being used by many laypeople (including Tyson) in the context of trans-related hormone therapy, Dr. Ole-Petter Hamnvik, an endocrinologist at Brigham and Women’s Hospital specializing in gender-affirming hormone therapy, tells Yahoo Life that it's not the preferred medical term. Most physicians, he explains, prefer using the term "gender-affirmation hormone therapy" as opposed to HRT as a way to specify the treatment.

"It's just easier to use 'gender-affirmation hormone therapy' so we can be very specific about what we're talking about regarding trans health care," he says.

Physical, mental and social impacts

Hamnvik says the majority of trans/nonbinary people on hormone therapy have seen immense "improvement in their emotional and mental wellbeing." Its use is supported by many leading healthcare organizations such as the American Psychiatric Association, the American Nurses Association and the World Medical Association. And research shows GAHT being associated with lower risks of suicide among trans youth.

"Some of that could be direct effects of the hormones on the brain," he surmises of the positive mental-health outcomes. "Some of that could also just be that people are responding positively to treatment and its physical changes, or just simply knowing they are taking hormones and that it's going to change their body in the right direction."

For transgender men on testosterone, physical changes include achieving a more masculine appearance (resulting in facial hair, a lower voice and other desired effects), while for transgender women on estrogen, the therapy helps to achieve a more feminine appearance (such as breast development, reduced body hair and a redistribution of body fat). When nonbinary people use hormone therapy, it's typically to masculinize or feminize their bodies in subtle ways to create a more androgynous appearance that is neither male nor female presenting.

"Some physical changes can happen fairly quickly, within a few months," Hamnvik notes. "But many of the changes take three to four years to be fully established, so it's a pretty slow process overall." (Some patients also prefer to "micro-dose" hormones for an even slower, gradual transition.)

Should someone choose to stop hormones, the degree to which the physical effects can be reversed depends on how long a patient has been taking them: For those taking estrogen, some breast growth, and possibly reduced or absent fertility, are not reversible. Similarly, for those taking testosterone, clitoral growth, facial hair growth, voice changes and male-pattern baldness are not reversible.

As far as side effects, besides possibly reduced fertility, a recent study from the American College of Cardiology found hormones may increase risks of stroke, heart attack and blood clots in some people.

Still, even when hormones bring about a desired effect, experiencing the change to your body in real time can be shocking and triggering for some. That's why, Hamnvik adds, physicians typically use "data-informed consent" when prescribing hormone therapy to adult patients, which "assumes that the adult is able to weigh the risks and benefits of a given intervention, and sort of make a decision about what's right for them." For adolescents, however, numerous "mental health evaluations" and "parental consents" are required, he explains.

"That being said, most of my patients come with an already established relationship with a therapist," he says. "I think that is oftentimes helpful for someone who's going to undergo what could be a life-changing intervention."

'Time to be patient'

Despite immense social progress, ongoing anti-trans sentiment has led to increased harassment against physicians who practice trans health care, which has been top of mind for doctors and patients alike.

"I just came out of my clinic, and in every single visit today the political situation came up as a concern for my patients," Hamnvik says. That's supported by the latest report from Trevor Project, an LGBTQ suicide prevention organization, showing that one in three queer youths' mental health was poor "most of the time or always" due to anti-LGBTQ policies and legislation in states like Alabama, Arkansas, Kentucky, Tennessee, Utah and West Virginia, among others, that have enacted laws limiting or banning gender-affirming care for minors.

Trans patients are increasingly anxious about the possibility of politicians taking away their "life-saving treatment," explains Hamnvik. "I've had patients who've decided to start gender-affirming interventions sooner than expected so they can get it done before it's potentially made illegal, which is what many people are fearing nationwide."

In the coming months, Hammvik remains concerned for "the mental health and wellbeing" of trans and nonbinary people living in states that are attacking their health care, which is why he says it's never been more important for other doctors to "provide the public with factual information about gender-affirming hormone therapy."

"People's lives are at stake, and we must support them," he adds.

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