Summary
Testosterone makes the body produce more red blood cells. Blood that becomes too thick raises the risk of clots, heart attack and stroke. Amsterdam doctors reviewed blood tests from 1,073 trans men on testosterone over up to 20 years. About one in nine had repeatedly high levels by male standards. The chance of ever crossing the limit kept rising for years, reaching 38% after a decade, so someone stable for years can still develop it. Long-acting injections, smoking, higher weight, older age and lung disease raised the risk. The authors advise checking blood for as long as testosterone is used. More than half of the clinic's trans men were left out for missing data. Using the normal limits for women would label far more people as affected (26%, the authors said in a reply to a letter), so the true scale may be higher.
Key findings
- Trong 1.073 nam chuyển giới dùng testosterone, 11% có máu quá đặc (hơn một nửa thể tích máu là hồng cầu) ở hai lần xét nghiệm theo tiêu chuẩn của nam; 3,7% và 0,5% vượt các giới hạn cao hơn.
- 24% có ít nhất một xét nghiệm máu vượt giới hạn của nam.
- Trung bình, tỷ lệ máu là hồng cầu tăng từ 39% trước điều trị lên 45% sau một năm, sau đó chỉ tăng nhẹ trong 20 năm.
- Trong 776 người có dữ liệu ban đầu, khả năng từng vượt giới hạn của nam đạt 38% sau 10 năm và 50% sau 14 năm.
- Thuốc tiêm testosterone tác dụng kéo dài có liên quan đến khả năng máu quá đặc cao gấp khoảng 3 lần so với gel; hút thuốc (khoảng gấp hai lần), cân nặng cao hơn, tuổi bắt đầu lớn hơn và các bệnh phổi cũng làm tăng nguy cơ.
- Nếu dùng giới hạn bình thường của nữ thay vào đó, 26% sẽ đủ điều kiện ở hai lần xét nghiệm, các tác giả cho biết trong một phản hồi cho một lá thư đã công bố.
- Nghiên cứu chỉ đo xét nghiệm máu, không đo các biến cố sức khỏe thực tế như cục máu đông hay đau tim.
Abstract
CONTEXT: Erythrocytosis is a known side effect of testosterone therapy that can increase the risk of thromboembolic events. OBJECTIVES: To study the prevalence and determinants in the development of erythrocytosis in trans men using testosterone. METHODS: A 20-year follow-up study in adult trans men who started testosterone therapy and had monitoring of hematocrit at our center (n = 1073). RESULTS: Erythrocytosis occurred in 11% (hematocrit > 0.50 L/L), 3.7% (hematocrit > 0.52 L/L), and 0.5% (hematocrit > 0.54 L/L) of trans men. Tobacco use (odds ratio [OR] 2.2; 95% CI, 1.6-3.3), long-acting undecanoate injections (OR 2.9; 95% CI, 1.7-5.0), age at initiation of hormone therapy (OR 5.9; 95% CI, 2.8-12.3), body mass index (BMI) (OR 3.7; 95% CI, 2.2-6.2), and pulmonary conditions associated with erythrocytosis and polycythemia vera (OR 2.5; 95% CI, 1.4-4.4) were associated with hematocrit > 0.50 L/L. In the first year of testosterone therapy hematocrit increased most: 0.39 L/L at baseline to 0.45 L/L after 1 year. Although there was only a slight continuation of this increase in the following 20 years, the probability of developing erythrocytosis still increased (10% after 1 year, 38% after 10 years). CONCLUSION: Erythrocytosis occurs in trans men using testosterone. The largest increase in hematocrit was seen in the first year, but also after the first years a substantial number of people present with hematocrit > 0.50 L/L. A reasonable first step in the care for trans men with erythrocytosis while on testosterone is to advise them to quit smoking, to switch to a transdermal administration route, and if BMI is high, to lose weight.
Conclusion
Erythrocytosis occurs in trans men using testosterone. The largest increase in hematocrit was seen in the first year, but also after the first years a substantial number of people present with hematocrit > 0.50 L/L. A reasonable first step in the care for trans men with erythrocytosis while on testosterone is to advise them to quit smoking, to switch to a transdermal administration route, and if BMI is high, to lose weight. The authors add that regular hematocrit control seems warranted for as long as testosterone is used.