Three cases of thyroid cancer in transgender female veterans receiving gender-affirming estrogen treatment

Background

Papillary thyroid cancers are relatively common endocrine malignancies. Risks include obesity, smoking, family history, and radiation exposure. Estrogens may be associated with an increased risk; the implications for transgender women, who use estrogen for gender-affirming hormone therapy (GAHT), are unclear.

Cases

3 transgender female veterans seen at sites within our VA Health System were diagnosed with papillary thyroid cancer. All three had started some form of estrogenic GAHT prior to the diagnosis, between 3 months to 5 years earlier. One veteran had radiation exposure, one had a smoking history, and 2 were obese. 2 were treated with thyroidectomy, and one had a recurrence treated with RAI. Each veteran had started GAHT before coming to the VA, and one started without physician support.

Discussion

Thyroid cancer prevalence in the transgender female population is not yet well-established. These 3 transgender female veterans each had risk factors associated with cancer development. Based on limited existing data, it is conceivable but not clear that GAHT treatment could have impacted their course.

Conclusion

Further investigation of thyroid cancer among transgender women in general, and into the impact of GAHT on disease burden in particular, is needed. Clinicians should also be aware that patients may be receiving hormonal therapy from nontraditional sources with unforeseen and unknown associated risks.