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Testosteron verhoogde rode bloedcellen bij transmannen: 38% overschreed binnen 10 jaar de mannelijke erytrocytosegrens

Erytrocytose in een groot cohort transmannen die testosteron gebruiken: een langetermijnvervolgstudie naar prevalentie, determinanten en blootstellingsjaren

Cohort- & registerstudiesCross-sekse hormonen
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

  • Van 1.073 transmannen op testosteron had 11% volgens mannelijke normen bij twee onderzoeken te dik bloed (meer dan de helft van het bloedvolume bestaand uit rode cellen); 3,7% en 0,5% overschreden hogere grenzen.
  • 24% had minstens één bloedonderzoek boven de mannelijke grens.
  • Gemiddeld steeg het aandeel van het bloed dat uit rode cellen bestaat van 39% vóór de behandeling naar 45% na een jaar, en steeg daarna over 20 jaar slechts weinig.
  • Onder de 776 mannen met beginwaarden bereikte de kans om ooit boven de mannelijke grens te komen 38% na 10 jaar en 50% na 14 jaar.
  • Langwerkende testosteroninjecties hingen samen met ongeveer 3 keer de kans op te dik bloed vergeleken met gel; roken (ongeveer twee keer de kans), hoger gewicht, hogere startleeftijd en longaandoeningen verhoogden ook het risico.
  • Met de normale grens voor vrouwen zou 26% bij twee onderzoeken in aanmerking zijn gekomen, zeiden de auteurs in een antwoord op een gepubliceerde brief.
  • De studie mat alleen bloedonderzoeken, niet daadwerkelijke gezondheidsgebeurtenissen zoals bloedstolsels of hartaanvallen.

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.