Based on emerging evidence and expert opinion, a task force put together by the International Society for Clinical Densitometry created position statements on the assessment of bone mineral density (BMD) in transgender and gender-nonconforming (TGNC) individuals. This report was published in the Journal of Clinical Densitometry.
The investigators performed a review of literature focused on the characterization of BMD in TGNC patients both before and after treatment with gender-affirming hormone therapy. Four positions were developed regarding bone densitometry in TGNC individuals and calculation of z scores. The task force elicited the opinions of experts in the management of TGNC individuals and representatives from the TGNC community.
Who Should Be Screened at Baseline?
Baseline BMD testing with dual-energy x-ray absorptiometry (DXA) is only indicated for TGNC individuals if they have a history of gonadectomy or have received therapy to lower endogenous gonadal steroid levels before starting gender-affirming hormone therapy, if they have hypogonadism with no plan to take hormone therapy, or if they meet existing indications for BMD testing, such as hyperparathyroidism or glucocorticoid use.
Although transgender women have lower BMD compared with cisgender men, there is no evidence that suggests that their risk for fracture is higher, and BMD is known to stabilize or increase in the long term with estrogen treatment. Transgender men have higher BMD compared with cisgender women, and testosterone therapy further increases BMD.
How Often Should Screening Be Repeated?
Follow-up BMD testing should be performed in TGNC individuals when the results are likely to affect patient management; for example, when an individual’s BMD is defined as low according to current guidelines. Follow-up testing may be appropriate for individuals receiving puberty-suppressing treatment (eg, gonadotropin-releasing hormone analogs), those with inadequate hormone doses or not adhering to hormone therapy, or for those planning to discontinue hormone therapy.
In addition, if other conditions that increase risk for bone loss or fragility fracture are suspected, follow-up testing is further indicated. The International Society for Clinical Densitometry recommends that BMD testing intervals should be based on the individual patient’s unique clinical status; however, testing every 1 to 2 years until BMD stabilizes or improves is appropriate. Following stabilization, longer intervals may be recommended.
What Reference Databases Should Be Used for Diagnosis?
The calculation of T-scores should follow guidelines that recommend using a uniform white (nonrace adjusted) female normative database for all patients, including transgender individuals of all ethnic groups. For TGNC individuals aged ≥50 years, T-scores ≤-2.5 should be used to diagnose osteoporosis regardless of hormonal status.
The calculation of z scores should use the appropriate normative database that matches the gender identity of the individual: the female database is suitable to calculate z scores in transgender women and the male database to calculate z scores in transgender men. Depending on the situation, the referring provider may adjust their assessment of an individual’s BMD in which z scores are also calculated using the normative database matching the sex recorded at birth.
In gender-nonconforming individuals whose identity is outside the gender binary, the normative database that matches the sex recorded at birth should be used, as no reference data on expected BMD or matching databases exist. To aid in the selection of the appropriate database, the International Society for Clinical Densitometry recommends implementing questions about gender identity on patient intake forms.
What Parameters Should Be Used in DXA Reports?
The DXA report used for transgender individuals should include the same parameters as that of the general population. However, because no matching databases currently exist for this population, providers may request the report include z scores calculated from both female and male databases.
Future research regarding BMD in TGNC individuals should investigate causes of low bone density in transgender women reported prior to hormone therapy, BMD characteristics in gender-nonconforming individuals, and how to best assess the risk for fracture in TGNC individuals.
“BMD measurement is not indicated in TGNC individuals unless there is an indication that would suggest a need for BMD measurement in a cisgender individual,” concluded the investigators.
Rosen HN, Hamnvik OPR, Jaisamrarn U, et al. Bone densitometry in transgender and gender nonconforming (TGNC) individuals: the 2019 ISCD official positions [published online July 10, 2019]. J Clin Densitom. doi:10.1016/j.jocd.2019.07.004