Three medical experts are pushing back on the increasingly common practice of using puberty blockers on children and teens struggling with gender dysphoria.

Their report, published Tuesday in the journal The New Atlantis, sheds light on what it calls the “radical” and “experimental” practice of using puberty suppression hormones on children as young as 9.

The paper, “Growing Pains: Problems with Puberty Suppression in Treating Gender Dysphoria,” is co-authored by Paul W. Hruz, a professor at Washington University School of Medicine; Lawrence S. Mayer, a scholar in residence at Johns Hopkins School of Medicine and a professor at Arizona State University; and Paul R. McHugh, university distinguished professor of psychiatry at Johns Hopkins University School of Medicine and the former psychiatrist-in-chief at Johns Hopkins.

Hruz, Mayer, and McHugh first point to a recent and dramatic increase in young people receiving treatment for gender identity issues. One of many examples they use: Gender Identity Development Service in the United Kingdom saw a 2,000 percent increase in referrals in seven years—from 94 children in 2009-2010 to 1,986 in 2016-2017.

While more and more gender-dysphoric children are getting treatment, the authors argue very little is known about the full spectrum of psychological and physical consequences stemming from puberty suppression and cross-sex hormone therapy.

While they often are pushed as a fully reversible, harmless, and cautionary treatment option, the reality, according to the authors, is that children, parents, and doctors are making decisions in scientific ignorance.

The paper challenges three key claims.

First, that the treatment is reversible. Puberty blockers are presented as a “let’s just hold off puberty” solution, meant to delay the development of the most prominent features of a child’s biological sex while the child wrestles with his or her gender identity. But Hruz, Mayer, and McHugh argue it remains unknown if regular sex-typical puberty will resume following suppression.

Indeed, “there are virtually no published reports, even case studies, of adolescents withdrawing from puberty-suppressing drugs and then resuming the normal pubertal development typical for their sex,” according to the authors.

Second, that the treatment is harmless.

“Puberty suppression hormones prevent the development of secondary sex characteristics, arrest bone growth, decrease bone accretion, prevent full organization and maturation of the brain, and inhibit fertility,” Hruz, Mayer, and McHugh write in a Supreme Court brief filed in the Gavin Grimm case. They go on to list other possible side effects of cross-gender hormones, oral estrogen, and testosterone, including sterility, coronary disease, cardiovascular disease, elevated blood pressure, and breast cancer.

Finally, that the treatment is cautionary.

The authors note the best, most-cited studies conclude most children with gender dysphoria come to embrace their birth sex. But Hruz, Mayer, and McHugh warn hormone therapy often solidifies a child’s gender dysphoria, driving him or her to persist in identifying as transgender, instead of allowing for the likely result: growing out of it.

“Gender identity for children is elastic (that is, it can change over time) and plastic (that is, it can be shaped by forces like parental approval and social conditions),” write the doctors, warning that if gender-affirming care causes children to continue identifying as the opposite sex, children will be exposed to hormonal and surgical interventions they otherwise would not need.

Instead of accepting hormone suppression without question, Hruz, Mayer, and McHugh instead recommend treating it like what it is: a radical experimental therapy carried out on children.