Low BMD z scores common among gender-affirming youths prior to treatment
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About 30% of a cohort of gender-diverse youths had low whole-body bone mineral density z scores prior to initiation of puberty blockers or gender-affirming hormones, according to findings published in Transgender Health.
In a retrospective analysis of data of youths who were treated at the gender clinic of Seattle Children’s Hospital Clinic, 89% had a whole-body BMD z score of zero or lower, and there was a difference in BMD z scores between those assigned male at birth and those assigned female at birth.
“In our study cohort, the patients assigned male at birth had much lower BMD compared to those assigned female at birth,” Juanita K. Hodax, MD, co-director of the gender clinic at Seattle Children’s Hospital, told Healio. “This has been shown in prior studies as well, but the degree of the difference in our study was larger than prior studies, and the reason for this is still unclear.”
Hodax and colleagues conducted a retrospective chart review of 64 patients younger than 19 years who attended the gender clinic at Seattle Children’s Hospital from October 2016 to May 2019 and had a DXA scan performed prior to using puberty blockers or gender-affirming hormones (73% assigned male at birth). BMD measurements at the whole body, whole body minus head, left femoral neck, left total hip and total lumbar spine were collected. BMD z scores at each site were calculated based on sex assigned at birth. Participants were classified as having low BMD if their z score was less than or equal to –2. Researchers also obtained bone age X-rays for 44 participants and 25-hydroxyvitamin D levels for all youths.
Of the cohort, 14% identified as male, 44% identified as female and 42% identified as nonbinary. Of those who had bone age X-rays performed, none had delayed bone age and three had advanced bone age.
Whole-body minus head BMD z scores were low for 30% of participants, between 0 and –2 in 59%, and greater than zero in 11%. Youths assigned male at birth had a greater portion of participants with a low whole-body minus head BMD z score compared with those assigned female at birth (36% vs. 12%). Low total lumbar spine BMD was observed in 17% of those assigned male at birth vs. 5% of patients assigned female at birth. Similar findings were observed with total whole-body, left femoral neck and left total hip BMD.
After adjusting for sex assigned at birth and age, increasing BMI, height and weight z scores were associated with higher BMD z scores. Hodax said the findings can be valuable for providers trying to identify gender-affirming youths with low BMD.
“When we know that someone is at risk for lower BMD, we can encourage them to take measures to improve BMD, such as increasing calcium and vitamin D intake and increasing exercise,” Hodax said.
The mean 25-(OH)D level in the cohort was 24 ng/mL, and 12 participants had low vitamin D levels of less than 20 ng/mL. Vitamin D was not associated with BMD z scores at any site.
Hodax noted more research is needed to analyze whether puberty blockers have any long-term effects on changes in BMD.
“The research that has been done in this area so far shows that BMD may decrease after starting puberty blockers, but increases after someone starts gender-affirming hormones,” Hodax said. “It would be helpful to have more data evaluating this for longer time frames.”
For more information:
Juanita K. Hodax, MD, can be reached at juanita.hodax@seattlechildrens.org.
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