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A year of hormones cuts testosterone 96%. Strength barely moves.

Bar chart of median change after about 12 months of hormones in transgender women: testosterone down 95.6%, hemoglobin down 7%, muscle size down 6.4%, lean body mass down 4%, strength up 0.5% (range -7.1% to +2%).

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Across adult study groups, a year of testosterone suppression and estrogen lowered testosterone by a median of about 96%, but lowered hemoglobin by 7%, muscle size by 6%, lean mass by 4%, and left strength essentially unchanged (median +0.5%; groups ranged from -7% to +2%).

Median percentage change after about 12 months of testosterone suppression and estrogen in adult transgender women, across the study groups in a 2021 systematic review. Bars show the median; whiskers show the lowest and highest study group.

Credit: FactHub Research Team; data from Harper et al., British Journal of Sports Medicine (2021), Tables 2-5

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Where this chart is used

What this chart asks

After a year of hormone treatment, how much do testosterone, hemoglobin, muscle size, lean mass and strength fall in transgender women?

Why it is shown this way

  • Bars on one zero-based axis put the fall in testosterone beside the much smaller changes in the body measures that drive performance.
  • Whiskers show the lowest and highest study group, so readers see the spread behind each median rather than a single study.
  • Medians of every adult 12-month study group in the review are used instead of one study, so no favorable study is picked.

Chart annotations

These markers provide relevant context for interpreting the chart. Their timing or position does not, by itself, establish causation.

No change
Threshold: 0

Why this is marked: Marks zero so readers can see that strength's median change is close to none.

Data and accessibility

Download chart data · Open accessible table · Download PNG · Download SVG

Dataset testosterone-suppression-athletic-measures, analysis twelve-month-change

Sources

This chart draws on the sources of the dataset versions it visualizes.

Transgender women on hormones: what changes in a year, and Air Force fitness tests over 2.5 years

  1. Harper J, O'Donnell E, Sorouri Khorashad B, McDermott H, Witcomb GL (British Journal of Sports Medicine) Systematic review, Tables 2-5: per-study changes in lean body mass, muscle cross-sectional area, strength and hemoglobin or hematocrit, with each study's testosterone before and after treatment, in transgender women on hormones. Free copy

    Retrieved November 5, 2026. CC BY 4.0. Open access under CC BY 4.0; FactHub republishes the extracted numbers with attribution.

    Reliability: Peer-reviewed study. Peer-reviewed systematic review of 24 studies of non-athletic transgender women, from Loughborough University and partners; no specific funding and no competing interests declared.

  2. Roberts TA, Smalley J, Ahrendt D (British Journal of Sports Medicine) Table 4: U.S. Air Force fitness-test push-ups, sit-ups and 1.5-mile run times of 46 transgender women before and during hormone treatment, compared with the average Air Force woman and man under 30.

    Retrieved November 5, 2026. Copyright BMJ; numbers reported as facts. FactHub republishes the table's means, differences and confidence intervals as facts, with attribution; the article text is not redistributed.

    Reliability: Peer-reviewed study. Peer-reviewed study of U.S. Air Force medical and fitness records, 2004-2018, by military and academic pediatricians; no specific grant. Fitness tests measure endurance, not maximal strength, and the comparison is to an Air Force average, not matched controls.

  3. Scharff M, Wiepjes CM, Klaver M, Schreiner T, T'Sjoen G, den Heijer M (Endocrine Connections) Cross-check of the largest 12-month study group: 249 transgender women in the European ENIGI cohort, grip strength 41.8 kg before and 40.0 kg after 1 year; median testosterone 17.9-18.5 nmol/L before and 0.4-0.8 nmol/L during treatment by clinic (Table 1). Free copy

    Retrieved November 5, 2026. CC BY 4.0. Open access; numbers republished with attribution.

    Reliability: Peer-reviewed study. Multicenter prospective clinical cohort in Amsterdam, Ghent and Oslo; authors declare no conflict of interest.

  4. Wiik A, Lundberg TR, et al. (Journal of Clinical Endocrinology & Metabolism) Cross-check of the Wiik study group: thigh muscle volume fell 5% and quadriceps cross-sectional area 4% in 11 transgender women after 12 months, while strength was maintained.

    Retrieved November 5, 2026. Copyright Endocrine Society; numbers reported as facts. Numbers republished as facts with attribution.

    Reliability: Peer-reviewed study. Prospective study of 11 untrained transgender women at Karolinska Institutet, Stockholm; funded by Stockholm County Council and two foundations; no conflicts declared.

Limitations

  • Adults, mostly untrained, in clinical studies; not athletes and not adolescents.
  • Each study group counts once regardless of size; 4 to 12 groups per measure.
  • Strength pools hand grip and knee strength; muscle size pools thigh, forearm and calf measurements.
  • About 12 months only; the review found strength, lean mass and muscle size still above women's at 36 months, with few studies.
Where this chart is used: version details

The exact citing versions, and the version of this chart each cites.

  • Article trans-girls-athletic-advantage — version 3 (published) cites version 1
  • Article trans-girls-athletic-advantage — version 2 (published) cites version 1

Node: chart:hormones-year-testosterone-vs-strength:1