Opponents of gender-affirming care for trans youth often claim that puberty blockers negatively impact young people’s bone density; something that sounds alarming considering that adolescence is the primary time of life when humans acquire their lifelong bone mass.
However, a study published today in the journal JAMA Pediatrics concluded that trans minors on puberty blockers experience only a “modest and uncertain” loss in bone density that is “partially recovered” when they begin gender-affirming hormone therapy.
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The study conducted a meta-analysis on 10 past independent studies (or “cohorts”) that included data on bone density among 751 trans minors — 427 of which had been assigned male at birth (AMAB) and 324 which had been assigned female at birth (AFAB). These studies, which all spanned about an average span of three years, looked at bone density within three different body sites: the five vertebrae of the spine’s lower lumbar region, the total hip, and the top of the femur (a part of the upper leg bone known as “the femoral neck”).
Bone growth in these sites among trans minors on puberty blockers slowed “numerically below [the] baseline” when compared to the usual growth seen among cisgender peers of the same age. Additionally, researchers found that these changes “were generally not statistically different across most skeletal sites,” MedPage Today reported, meaning that any losses occurred consistently throughout the tested sites rather than in just one area.
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Any loss in bone density was compounded by the fact that puberty blockers’ reduce users’ non-fat body tissues (referred to as “lean mass”) and increase their fat mass. These bodily changes can impair interactions between bone and muscle that influence skeletal development during puberty.
Researchers found that any loss in bone density was “at most a modest and uncertain shortfall in catch-up rather than a demonstrated persistent deficit,” meaning that it was slight, temporary, and began to recover when patients began receiving hormone replacement therapy associated with their gender identity.
“Across different cohorts and healthcare settings, we observed the same overall trajectory: bone mineral density increased and bone accrual resumed after the introduction of sex steroids,” said researcher Daniele Tienforti, MD.
The study also found that bone density was generally higher among trans minors who had a higher body mass index (an estimate of body fat based on a person’s height and weight), those who used puberty blockers for shorter amounts of time or started them at an older age, and those who had longer exposure to hormone replacement therapy.
Despite this, Tienforti acknowledged that the study has several limitations, including a lack a follow-up data among the young patients in each study, a lack of comparative cisgender patient data, and a lack of data on how other body chemicals or fractures might have impacted each minor’s bone development.
Nevertheless, Tienforti said that gender-affirming healthcare providers should routinely monitor young people’s bone health throughout treatment.
“Rather than focusing on a single phase of treatment, I think it’s important to view skeletal development as a dynamic process that deserves ongoing attention throughout care,” Tienforti said. He added that healthcare workers can advise patients to focus on modifiable lifestyle factors — like calcium and vitamin D intake, weightlifting exercises, and x-rays of bone density — tailoring each patient’s exposure to gender-affirming medications.
While gender-affirming medications have safely been used for decades on children with early onset puberty, hormone disorders, and rare cancers, opponents of gender-affirming care protest that these medications can have negative lifelong side effects.
For example, the organization Genspect published an article on its website claiming, “Puberty blockers and cross-sex hormones negatively impact bone health in a significant number of cases.” The four-paragraph article is unsigned and references only five studies without extensively explaining any of them.
But even though Genspect describes itself as a non-partisan organization, civil rights organizations like the Southern Poverty Law Center have classified it as right-wing or anti-LGBTQ+ due to its members active opposition to gender-affirming care, trans journalist Erin Reed noted.
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