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Testosteron erhöhte rote Blutkörperchen bei trans Männern: 38 % überschritten binnen 10 Jahren die männliche Grenze

Erythrozytose in einer großen Kohorte von trans Männern unter Testosteron: eine Langzeit-Nachbeobachtungsstudie zu Prävalenz, Determinanten und Expositionsjahren

Kohorten- & RegisterstudienKörperfremde Hormone
Authors
Milou Cecilia Madsen, Dennis van Dijk, Chantal M. Wiepjes, Elfi B. Conemans, Abel Thijs, Martin den Heijer
Journal
The Journal of Clinical Endocrinology & Metabolism
Year
2021
Source
https://doi.org/10.1210/clinem/dgab089

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

  • Von 1.073 trans Männern unter Testosteron hatten 11 % nach männlichen Maßstäben bei zwei Tests zu dickes Blut (mehr als die Hälfte des Blutvolumens aus roten Blutkörperchen); 3,7 % und 0,5 % überschritten höhere Grenzwerte.
  • 24 % hatten mindestens einen Bluttest über dem männlichen Grenzwert.
  • Im Durchschnitt stieg der Anteil des Blutes aus roten Blutkörperchen von 39 % vor der Behandlung auf 45 % nach einem Jahr und stieg dann über 20 Jahre nur leicht.
  • Bei den 776 Männern mit Ausgangsdaten erreichte die Wahrscheinlichkeit, je über den männlichen Grenzwert zu gehen, nach 10 Jahren 38 % und nach 14 Jahren 50 %.
  • Langwirksame Testosteronspritzen hingen mit etwa 3-fachen Chancen auf zu dickes Blut im Vergleich zu Gel zusammen; Rauchen (etwa doppelte Chancen), höheres Gewicht, höheres Startalter und Lungenerkrankungen erhöhten das Risiko ebenfalls.
  • Bei Verwendung des normalen Grenzwerts für Frauen hätten 26 % bei zwei Tests dazugezählt, sagten die Autoren in einer Antwort auf einen veröffentlichten Brief.
  • Die Studie maß nur Bluttests, keine tatsächlichen Gesundheitsereignisse wie Blutgerinnsel oder Herzinfarkte.

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.