P-685 Discrepancies in Bone Age Assessment of Transgender Adolescents: Impact of Gender Assignment on Measurement Accuracy

Study question

How does the use of affirmed gender instead ASAB in bone age assessment affect measurement accuracy in transgender adolescents undergoing hormone suppression therapy (GnRHa)?

Summary answer

Using affirmed gender in bone age assessment of TGD adolescents leads to statistically significant, gender-specific biases, potentially impacting clinical decision-making and long-term skeletal health outcomes.

What is known already

Accurate bone age assessment is crucial for optimal endocrine management of transgender and gender diverse (TGD) adolescents undergoing hormone suppression therapy (GnRHa). The Greulich and Pyle method is commonly used for bone age assessment, with separate standards for males and females. However, there is a lack of standardized guidelines for bone age assessment in TGD adolescents, leading to inconsistencies in whether assigned sex at birth (ASAB) or affirmed gender standards are used. This variability raises concerns about measurement accuracy and its potential impact on clinical decision-making.

Study design, size, duration

This retrospective study analyzed bone age assessments of 41 TGD adolescents (mean age 15.07 years ±SD; 26 transgender boys, 15 transgender girls) undergoing GnRHa. Hand-wrist radiographs were evaluated using both ASAB and affirmed gender standards based on the Greulich and Pyle method. Initial measurements and subsequent measurements (for 16 patients) were included in the analysis. The study duration spanned the period of GnRHa therapy for the cohort.

Participants/materials, setting, methods

Participants were 41 TGD adolescents receiving care at the Department of Gynecological Endocrinology and Reproductive Medicine at the University Hospital Innsbruck. Bone age was assessed using the Greulich and Pyle method, applying both ASAB and affirmed gender standards. All radiographs initially evaluated using affirmed gender standards were re-analyzed using ASAB criteria. Paired t-tests were conducted to compare the measurements and determine the statistical significance of observed differences between ASAB and affirmed gender assessments.

Main results and the role of chance

At initial bone age measurement, only 63% (26/41) of TGD adolescents were evaluated using ASAB, while 37% (15/41) used affirmed gender. In subsequent measurements of 16 patients, affirmed gender use increased to 87.5% (14/16). Re-evaluation of cases where affirmed gender was used revealed statistically significant gender-specific biases.For assigned females at birth (AFAB, n = 11), bone age measurements using affirmed gender were on average 1.18 units higher than ASAB (p < 0.001). For assigned males at birth (AMAB, n = 4), measurements using affirmed gender were 1.5 units lower than ASAB (p < 0.05).

This consistent pattern of measurement bias could significantly impact clinical decision-making, particularly in timing interventions and monitoring skeletal health during hormone suppression therapy. Our findings underscore the urgent need for standardized, evidence-based guidelines for bone age assessment in TGD adolescents to optimize long-term health outcomes

Limitations, reasons for caution

The retrospective design and small sample size, particularly for AMAB individuals (n = 4), limit generalizability. The Greulich-Pyle method’s inherent subjectivity and potential inter-observer variability warrant caution. Prospective studies with larger cohorts are needed to confirm findings and assess long-term implications. Potential confounding factors (e.g., BMI, vitamin D status) were not addressed.

Wider implications of the findings

These findings emphasize the critical need for standardized, evidence-based guidelines for boneage assessment in TGD adolescents. Inaccurate assessments may result in suboptimal treatment timing, potentially impairing growth trajectories and skeletal health. Developing specific protocols tailored to TGD individuals will enhance clinical decision-making, ensuring accurate monitoring and improved long-term health outcomes.

Trial registration number

No