Purpose: Gender-affirming hormone therapy (GAHT) is safe overall, with few adverse effects. One potential effect from using testosterone for GAHT is an increase in hemoglobin and/or hematocrit, known as secondary erythrocytosis. Current guidelines recommend monitoring hemoglobin or hematocrit routinely in the first year, some as frequently as every 3 months, which can create barriers to care. Our study explored the incidence of erythrocytosis in the first 20 months of testosterone therapy among people receiving gender-affirming care.
Methods: This is a descriptive fixed cohort study of hematocrit and hemoglobin data from the charts of 282 people taking testosterone for GAHT.
Results: During the first 20 months of testosterone therapy, the cumulative incidence of hematocrit >50.4% was 12.6%, hematocrit >52% was 1.0%, and hematocrit >54% was 0.6%. All people were taking injectable testosterone cypionate, with a median dose of 100 mg weekly.
Conclusion: Severe erythrocytosis (hematocrit >54%) is a rare outcome of gender-affirming testosterone therapy. Clinical recommendations should reconsider the need for routine frequent erythrocytosis screening within the first year of testosterone therapy for patients who prefer to minimize laboratory draws.
Keywords: erythrocytosis; gender affirming care; gender affirming hormone therapy; guideline; testosterone; transgender.
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