Medical experts are sounding an urgent warning about heightmaxxing, a social media trend in which adolescents reportedly pursue extra height through dangerous medical experimentation. Reports say teenage boys are obtaining erdafitinib, a prescription cancer drug, from the black market and taking it without physician supervision.

Erdafitinib, referred to online as “ERDA” or “Erta,” is approved to treat advanced bladder cancer. Teenagers are reportedly experimenting with the medication after encountering internet discussions suggesting that it could make them taller.

“It’s extremely concerning that teenagers are experimenting with powerful cancer medications in an attempt to grow taller,” Dr. Stephanie Widmer, a New York City emergency medicine physician and Fox News medical contributor, told Fox News Digital.

“These drugs were developed to treat serious medical conditions, not to enhance physical appearance, and taking them without a legitimate medical indication or physician supervision can have devastating consequences.”

Johnson & Johnson also rejected the practice in a statement to Rolling Stone. The drugmaker emphasized that erdafitinib has never been approved to stimulate height growth and that its safety and effectiveness have not been established for pediatric or adolescent use.

The online interest appears connected to medical reports describing unexpected growth among children who received erdafitinib for brain tumors. A 2024 study published in Hormone Research in Paediatrics described accelerated growth in two pediatric patients.

A separate case report documented a teenager who grew more than 5 inches during treatment. That growth, however, was accompanied by serious skeletal complications, highlighting the danger of treating an unexpected drug effect as a cosmetic opportunity.

Physicians caution that these spurts do not represent healthy skeletal growth. Dr. Jessica Gray, a family physician in Lubbock, Texas, warned that forced and rapid growth can cause dangerous structural problems, including premature growth plate damage and bone fractures.

Widmer explained during an appearance on Fox News’ “America’s Newsroom” that the drug blocks specific cellular signaling pathways involved in cancer cell growth. Those pathways also play a role in bone development, which may help explain the unexpected growth seen in some pediatric patients.

Height is overwhelmingly governed by genetics, Widmer noted, and there are no biological shortcuts. Once growth plates close near the end of puberty, medications cannot reopen them, leaving older adolescents exposed to catastrophic health hazards without any chance of gaining height, she said.

“One of the biggest concerns is that these medications can cause serious side effects, including potentially permanent vision damage, elevated phosphate levels and other metabolic abnormalities,” Widmer said.

“We’re talking about adolescents whose bodies are still developing, and exposing them to these risks for a cosmetic goal is particularly troubling.”

Other warning signs and side effects associated with the medication include skeletal pain, particularly in the hips or knees. Mouth sores, loose nails and skin disorders have also been linked to the drug.

The heightmaxxing trend has intensified concerns about social media’s influence over teenagers’ health decisions. Widmer said online conversations focused on physical appearance and self improvement can expose young men to potentially unsafe practices that lack medical evidence.

“Parents need to understand that this goes beyond teenagers being insecure about their height,” Widmer said. “We’re talking about young people potentially obtaining prescription cancer medications and experimenting with them outside of medical supervision.”

Doctors advise parents to watch for symptoms such as unusual joint pain or unexplained physical changes and to speak with children if they suspect medications are being obtained online. Teenagers who are worried about their height or growth should consult a pediatrician before considering any medication.

“If a child has concerns about their growth, that conversation belongs in a pediatrician’s office, not on an internet forum,” Widmer said. “No amount of additional height is worth risking permanent damage to your vision or other serious and potentially unknown medical complications.”