A case for routine vitamin D supplementation in adults on gender affirming hormone therapy: results of a tertiary clinic audit — ASN Events
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A case for routine vitamin D supplementation in adults on gender affirming hormone therapy: results of a tertiary clinic audit (#361)

Sarah Lum 1 2 3 , Rita Upreti 3 4
  1. Centre for Endocrinology and Reproductive Health, Hudson Institute of Medical Research, Melbourne, VIC, Australia
  2. Department of Molecular and Translational Science, Monash University, Melbourne, VIC, Australia
  3. Department of Endocrinology and Diabetes , Monash Health, Melbourne, VIC, Australia
  4. Monash University, Melbourne, VIC, Australia

Background

Approximately 0.9% of Australians aged ≥16 years identify as transgender or gender diverse (collectively referred to as transgender in this study). For those wishing to pursue gender-affirming hormone therapy (GAHT), quality of life and gender dysphoria are significantly improved. Concerns about long-term GAHT impact on bone mineral density have been raised. Vitamin D testing in Australia in 2024 cost approximately $161.7 million, with 76.5% of tests estimated to deliver no clinical benefit. The 2024 Endocrine Society guidelines recommend empiric supplementation over routine testing in high-risk groups. No guidelines currently address vitamin D management specifically in transgender adults receiving GAHT.

Aims

To evaluate vitamin D testing practices and baseline deficiency prevalence in transgender adults receiving GAHT at a tertiary gender endocrinology clinic, and to assess testing costs to inform evidence-based practice recommendations.

Methods

A retrospective audit of 200 transgender adults attending a tertiary gender endocrinology clinic during 2025. Vitamin D tests ordered in these patients from 2020 – 2025 were reviewed. Age, gender identity, baseline vitamin D status, supplementation practices, and concordance with Australian Medicare Benefits Schedule (MBS) criteria were recorded. Testing costs were estimated using MBS data.

Results

Among 200 patients (median age 28 years; 41.5% trans women; 44% trans men; 14.5% non-binary or other gender identity), 864 vitamin D tests were ordered over five years. Only 202 tests (23.4%) met MBS criteria. At baseline, 60.5% had vitamin D deficiency (<50 nmol/L), and 68.5% were taking or recommended supplementation. Estimated cost of potentially low-value testing was AUD $19,893 in this cohort.

Conclusion

Vitamin D deficiency prevalence is high in transgender adults. Our findings suggest routine testing provides minimal clinical value. Consistent with the 2024 Endocrine Society guidelines for other at-risk populations, we recommend empiric vitamin D supplementation for transgender adults receiving GAHT as a cost-effective and clinically appropriate alternative.