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Cited by 206Hormonal and reproductive studiesLGBTQ Health, Identity, and PolicySports, Gender, and Society

The DOI matches its Crossref record; 66 of the 66 references it cites were found in a registry or an index; 53 of the 107 sources its claims cite were checked for support.

How does hormone transition in transgender women change body composition, muscle strength and haemoglobin? Systematic review with a focus on the implications for sport participation

Open access
Harper, Joanna, O'Donnell, Emma, Sorouri Khorashad, Behzad, McDermott, Hilary, Witcomb, Gemma L·2021·British Journal of Sports Medicine
DOI 10.1136/bjsports-2020-103106PMC PMC8311086
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Abstract

Objectives: We systemically reviewed the literature to assess how long-term testosterone suppressing gender-affirming hormone therapy influenced lean body mass (LBM), muscular area, muscular strength and haemoglobin (Hgb)/haematocrit (HCT). Design: Systematic review. Data sources: Four databases (BioMed Central, PubMed, Scopus and Web of Science) were searched in April 2020 for papers from 1999 to 2020. Eligibility criteria for selecting studies: Eligible studies were those that measured at least one of the variables of interest, included transwomen and were written in English. Results: Twenty-four studies were identified and reviewed. Transwomen experienced significant decreases in all parameters measured, with different time courses noted. After 4 months of hormone therapy, transwomen have Hgb/HCT levels equivalent to those of cisgender women. After 12 months of hormone therapy, significant decreases in measures of strength, LBM and muscle area are observed. The effects of longer duration therapy (36 months) in eliciting further decrements in these measures are unclear due to paucity of data. Notwithstanding, values for strength, LBM and muscle area in transwomen remain above those of cisgender women, even after 36 months of hormone therapy. Conclusion: In transwomen, hormone therapy rapidly reduces Hgb to levels seen in cisgender women. In contrast, hormone therapy decreases strength, LBM and muscle area, yet values remain above that observed in cisgender women, even after 36 months. These findings suggest that strength may be well preserved in transwomen during the first 3 years of hormone therapy.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This systematic review of 24 studies found that gender-affirming hormone therapy in transwomen rapidly lowers haemoglobin/haematocrit to cisgender female levels, while strength, lean body mass and muscle area decrease more slowly and remain above cisgender female values even after 36 months. The authors conclude that transwomen may retain strength advantages over cisgender women during the first 3 years of hormone therapy.

Key findings

  • Twenty-four studies were reviewed; transwomen experienced significant decreases in all measured parameters, but with different time courses. After 4 months of hormone therapy, Hgb/HCT levels were equivalent to those of cisgender women; after 12 months, significant decreases in strength, LBM and muscle area were observed.
  • LBM decreased by 3.0%–5.4% following hormone transition (p<0.05) in seven studies, and muscle CSA decreased by 1.5%–11.7% over 12–36 months. Strength reductions after 12 months ranged from non-significant to 7.1%, with the largest ENIGI study (n=249) reporting a 4.3% reduction (p<0.001).
  • Hgb/HCT decreased by 4.6%–14.0% (p<0.01) in eight studies. Cross-sectional comparisons found transwomen after ≥48 months of GAHT had 17% lower LBM, 24% smaller CSA and 24% lower hand grip/quadriceps strength than cisgender men, yet values for strength, LBM and muscle area remained above those of cisgender women even after 36 months.

Methods

  • Systematic review conducted in line with PRISMA guidelines; four databases (BioMed Central, PubMed, Scopus, Web of Science) were searched in April 2020 for papers from 1999 to 2020. Eligible studies measured at least one variable of interest, included transwomen and were written in English.
  • Twenty-four studies were included, with sample sizes from 12 to 249. Designs included 13 follow-up studies, 2 follow-up plus cross-sectional studies, 6 cross-sectional studies and 3 prospective studies. Quality was assessed with the EPHPP tool; all studies were categorised as moderate quality.
  • Data were extracted on lean body mass, muscle cross-sectional area, muscular strength and haemoglobin/haematocrit. Meta-analysis was not possible due to overlapping participants in the ENIGI studies and heterogeneous methodology.

Limitations

  • The paper states that the effects of GAHT on athletic performance in transgender people who train and compete remain unknown; physical activity levels were not reported; studies were English-only and conducted in Western countries, contributing to geographical bias; sparse data risk existed due to small sample sizes and short study durations; participant overlap and heterogeneous methodology precluded meaningful meta-analysis; and the review only focused on binary transgender individuals, not non-binary individuals.
  • The text makes evident that most included participants were non-athletic, many data were extracted from medical charts (nine studies from the same research group), posing risk of selective data reporting and publication bias, and five studies had post-GAHT testosterone values greater than 5 nmol/L, a possible confounder, with four of these in adolescent transfemales.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1136/bjsports-2020-103106

Cites

66 of 66 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

53 of 107 cited sources checked · 17 supported · 4 flagged · accuracy not yet measured

  • Findingcitation

    Seven of the follow-up studies, including the large ENIGI study, and two studies with high post-GAHT testosterone, showed that total lean body mass was decreased by 3.0%-5.4% following hormone transition (p<0.05).

    “Seven of these studies,15 36 39–41 44 51 including the large (n=179) ENIGI study,15 and two studies40 51 with high post-GAHT testosterone (~8 nmol/L), showed that total LBM was decreased by 3.0%–5.4% following hormone transition (p<0.05).”
    Quote in the paperSubstantial claim3 of 3 sources checked
    • cites [15] source
    • cites [36] Wierckx, 2014, Cross-sex hormone therapy in trans persons is safe and effective at short-time follow-up: results from the European network for the investigation of gender incongruence, J Sex Med source

      The Trans Women results report a decrease in total body lean mass after treatment, and Table 3 (page not available) shows significant decreases in both estrogen-treatment groups at 12 months (P<0.001 and P=0.02). But Table 3 lists 53 trans women and 53 trans men, not a follow-up sample of 179; this paper also cannot substantiate the results attributed to the other six studies or the two studies described as having high post-GAHT testosterone. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [39] Auer, 2018, Effects of sex hormone treatment on the metabolic syndrome in transgender individuals: focus on metabolic cytokines, J Clin Endocrinol Metab source

      The Markers of the MS section reports that lean mass remained unchanged in transwomen and increased in transmen after GAHT, contrary to the attributed decrease. The Patients section describes a cohort of 69, not the n=179 ENIGI study named in the citing sentence. No page numbers are available in our copy. (LLM, conf=0.90)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
  • Premisecitation

    In cisgender males, increases in testosterone due to puberty promote muscular strength in association with increased muscle cross-sectional area and increased lean muscle mass.

    “In cisgender males, increases in testosterone due to puberty promote muscular strength in association with increased muscle CSA, and increased lean muscle mass.26”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [26] source

      The Introduction and Discussion say that male puberty brings greater muscle mass and strength, and that testosterone increases both. The Discussion also refers to increased muscular size, but our copy does not specifically establish an increase in muscle cross-sectional area (CSA). (LLM, conf=0.83)

      Experimental — accuracy not yet measured
  • Premisecitation

    Testosterone exerts erythrogenic effects that result in increases in both haematocrit and haemoglobin.

    “Testosterone exerts erythrogenic effects that results in increases in both HCT and Hgb.23”
    Quote in the paperSubstantial claim1 of 1 sources checked
  • Premisecitation

    Low haemoglobin or low haematocrit can lead to a diminished supply of oxygen to the tissues and therefore have a direct effect on endurance performance.

    “Low Hgb, or low HCT, the volume of red blood cells compared with total blood volume, can lead to a diminished supply of oxygen to the tissues, and therefore have a direct effect on endurance performance.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [20] source

      The Methods describe hematocrit values used to prepare red-cell samples, and the Results examine hemoglobin removal from erythrocyte membranes (page numbers unavailable). Neither those passages nor searches for oxygen transport, tissue oxygen supply, anemia, or exercise address the claimed effect on endurance performance. (LLM, conf=0.77)

      Experimental — accuracy not yet measured
  • Findingcitation

    One study of adolescent participants who only reached a final testosterone level of 8.8 nmol/L exhibited forearm and calf cross-sectional area decreases of 4.1% and 8.9%, respectively.

    “One of these studies40 examined adolescent participants who only reached a final testosterone level of 8.8 nmol/L and exhibited forearm and calf CSA decreases of 4.1% and 8.9%, respectively.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [40] Tack, 2018, Proandrogenic and antiandrogenic progestins in transgender youth: differential effects on body composition and bone metabolism, J Clin Endocrinol Metab source

      The Body composition and grip strength section reports decreased forearm and lower-leg muscle area in adolescent trans girls. Table 2 gives their final mean testosterone as 253.35 ng/dL, approximately 8.8 nmol/L. Our copy does not report the claimed 4.1% and 8.9% decreases, so those magnitudes cannot be verified. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
  • It may state two separate claims as one. 27
  • Probably not a substantial claim. 10
  • The quote only partly states this claim. 1

  • It may state two separate claims as one.

    Study design and conductreasoning

    Aside from the three prospective studies, data were extracted from medical charts (nine of which were from the same research group), posing a risk of selective data reporting and publication bias.

    “Aside from these three studies, data were extracted from medical charts (nine of which were from the same research group,15 17 19 36–41) posing a risk of selective data reporting and publication bias.”
    Quote in the paperNot a substantial claim3 of 3 sources checked
    • cites [15] source

      The Study population and study design section (page unavailable) identifies this as a prospective observational study and describes scheduled clinic visits for data collection. That contradicts treating this paper as one of the studies whose data were extracted from medical charts. The paper does not establish the claim about nine studies from one research group or the resulting bias risk. (LLM, conf=0.85)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
    • cites [17] Scharff, 2019, Change in grip strength in trans people and its association with lean body mass and bone density, Endocr Connect source

      The Materials and methods section (Study design and study population; page not provided) identifies this paper as part of a multicenter prospective cohort, with measurements taken at baseline and follow-up. That contradicts its apparent inclusion among studies whose data were extracted from medical charts. The paper does not establish the citing sentence’s count of nine studies or its publication-bias assessment. (LLM, conf=0.86)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
    • cites [19] Defreyne, 2018, Prospective evaluation of hematocrit in gender-affirming hormone treatment: results from European network for the investigation of gender incongruence, Andrology source

      The Methods (page unavailable) identify this paper as a multicenter prospective cohort study with scheduled follow-up visits and blood sampling, not a study based on data extracted from medical charts. The Discussion (page unavailable) likewise calls it a prospective study. This paper therefore does not support classifying it among the chart-based studies; it does not assess the claimed count of nine or publication-bias risk across those studies. (LLM, conf=0.86)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured

  • It may state two separate claims as one.

    Premisecitation

    Studies in non-athletic transwomen undergoing gender-affirming hormone treatment report changes in lean body mass, muscle cross-sectional area, muscular strength, and haemoglobin and/or haematocrit.

    “However, studies in non-athletic transwomen undergoing GAHT also report changes in lean body mass (LBM),15 muscle cross-sectional area (CSA),16 muscular strength17 and haemoglobin (Hgb)18 and/or haematocrit (HCT).19”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites [15] source
    • cites [16] Wiik, 2020, Muscle strength, size, and composition following 12 months of Gender-affirming treatment in transgender individuals, J Clin Endocrinol Metab source
    • cites [17] Scharff, 2019, Change in grip strength in trans people and its association with lean body mass and bone density, Endocr Connect source

  • It may state two separate claims as one.

    Findingown data

    Three large ENIGI studies published in 2018 and 2019 contained much novel data, but also included many participants from previous studies, making it impossible to accurately state the number of unique participants.

    “Three large studies from the ENIGI group published in 2018 and 201915 17 19 contained much novel data, but also included many participants from previous studies making it impossible to accurately state the number of unique participants.”
    Quote in the paperNot a substantial claim3 of 3 sources checked
    • cites [15] source

      The Study population and study design section (page unavailable) identifies this as an ENIGI study and reports 341 participants, a larger body-composition study population than any before it. It does not say that participants overlapped with previous studies or that the number of unique participants across the cited studies cannot be determined. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [17] Scharff, 2019, Change in grip strength in trans people and its association with lean body mass and bone density, Endocr Connect source

      The Study design and study population section (page not available) identifies this as an ENIGI cohort study and reports 527 participants in its analyses. It does not establish how many participants appeared in earlier studies or say that the number of unique participants across the cited studies cannot be determined. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [19] Defreyne, 2018, Prospective evaluation of hematocrit in gender-affirming hormone treatment: results from European network for the investigation of gender incongruence, Andrology source

      The Methods and Results (page numbers unavailable) identify this as a large ENIGI study and report its analyzed participant counts. The Discussion describes a novel comparison. Our copy does not establish that participants overlapped with previous studies or that the number of unique participants across the three studies cannot be determined. (LLM, conf=0.84)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductcitation

    This systematic review was conducted in line with PRISMA guidelines.

    “This systematic review was conducted in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.32”
    Quote in the paperNot a substantial claim1 of 1 sources checked

  • It may state two separate claims as one.

    Findingcitation

    Two ENIGI studies found no significant strength differences, although one of these studies was carried out on adolescents who failed to reach typical female testosterone levels (8.8 nmol/L after GAHT).

    “Two ENIGI studies37 40 found no significant strength differences, although one of these studies40 was carried out on adolescents who failed to reach typical female testosterone levels (8.8 nmol/L after GAHT).”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [37] Auer, 2016, 12-Months metabolic changes among gender dysphoric individuals under cross-sex hormone treatment: a targeted metabolomics study, Sci Rep source

      The Patient population section identifies this as an ENIGI study, but the Methods and Results passages describe metabolite, body-composition, and hormone measurements, not strength outcomes. Searches for strength differences, adolescents, and 8.8 nmol/L found no passage supporting the cited claim; pages are not specified in our copy. (LLM, conf=0.76)

      Experimental — accuracy not yet measured
    • cites [40] Tack, 2018, Proandrogenic and antiandrogenic progestins in transgender youth: differential effects on body composition and bone metabolism, J Clin Endocrinol Metab source

      The Body composition and grip strength section reports no significant change in grip strength among trans girls during the study, but it does not report no strength differences between groups. Table 2 reports mean total testosterone of 253.35 ng/dL after cyproterone acetate treatment in trans girls, approximately 8.8 nmol/L. The paper describes this as progestin treatment, not GAHT. (LLM, conf=0.85)

      Experimental — accuracy not yet measured

  • It may state two separate claims as one.

    Findingcitation

    The largest ENIGI study (n=249) and one other study found significant reductions in hand grip strength (4.3% and 7.1%, respectively) after 12 months on GAHT (p<0.001).

    “The largest of the three (n=249) ENIGI studies17 and one other study41 found significant (p<0.001) reductions (4.3% and 7.1%, respectively) after 12 months on GAHT.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [17] Scharff, 2019, Change in grip strength in trans people and its association with lean body mass and bone density, Endocr Connect source
    • cites [41] Van Caenegem, 2015, Preservation of volumetric bone density and geometry in trans women during cross-sex hormonal therapy: a prospective observational study, Osteoporos Int source

  • It may state two separate claims as one.

    Findingcitation

    Although the transwomen in most of the studies achieved testosterone levels within the reference range for cisgender women, there were five studies in which the transfemales had post-GAHT testosterone values greater than 5 nmol/L.

    “Although the transwomen in most of the studies achieved testosterone levels within the reference range for cisgender women, there were five studies38 40 47 49 51 in which the transfemales had post-GAHT testosterone values greater than 5 nmol/L.”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [38] Tack, 2017, Consecutive cyproterone acetate and estradiol treatment in Late-Pubertal transgender female adolescents, J Sex Med source
    • cites [40] Tack, 2018, Proandrogenic and antiandrogenic progestins in transgender youth: differential effects on body composition and bone metabolism, J Clin Endocrinol Metab source
    • cites [47] source

  • It may state two separate claims as one.

    Premisecitation

    Typical haemoglobin values differ between males and females, with normal values ranging between 131-179 g/L for men and 117-155 g/L for women.

    “Typical values for Hgb differ between males and females, with ‘normal’ values ranging between 131–179 g/L for men and 117–155 g/L for women.21”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [21] source

      The Review introduction gives 14 g/dL as an example of normal haemoglobin concentration in men, but does not provide a male reference range or a female value. Searches for the stated endpoints and sex-specific normal ranges found no passage establishing 131–179 g/L for men or 117–155 g/L for women. (LLM, conf=0.77)

      Experimental — accuracy not yet measured

  • It may state two separate claims as one.

    Findingcitation

    Nine studies reported Hgb or HCT levels in transwomen before and after GAHT, with follow-up from a minimum of 3 to a maximum of 36 months post hormone therapy.

    “Nine studies16 19 36–38 43 47–49 reported the levels of Hgb or HCT in transwomen before and after GAHT, from a minimum of three to a maximum of 36 months post hormone therapy.”
    Quote in the paperNot a substantial claim3 of 5 sources checked
    • cites [16] Wiik, 2020, Muscle strength, size, and composition following 12 months of Gender-affirming treatment in transgender individuals, J Clin Endocrinol Metab source
    • cites [19] Defreyne, 2018, Prospective evaluation of hematocrit in gender-affirming hormone treatment: results from European network for the investigation of gender incongruence, Andrology source
    • cites [36] Wierckx, 2014, Cross-sex hormone therapy in trans persons is safe and effective at short-time follow-up: results from the European network for the investigation of gender incongruence, J Sex Med source
    • cites [37] Auer, 2016, 12-Months metabolic changes among gender dysphoric individuals under cross-sex hormone treatment: a targeted metabolomics study, Sci Rep source
    • cites [38] Tack, 2017, Consecutive cyproterone acetate and estradiol treatment in Late-Pubertal transgender female adolescents, J Sex Med source

  • It may state two separate claims as one.

    Premisecitation

    Cisgender women demonstrate 31% lower lean body mass, 36% lower hand-grip strength, and 35% lower knee extension strength than cisgender men.

    “cisgender women demonstrating 31% lower LBM,59 36%60 lower hand-grip strength and 35%61 lower knee extension strength than cisgender men”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites [59] source

      The Results report that men had, on average, 18 kg more lean body mass than women, supporting the direction of the comparison. Our copy does not give the cited 31% figure or establish that participants were cisgender. The hand-grip and knee-extension figures have separate citations and are not attributed to this paper. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [60] Bohannon, 2019, Handgrip strength: a comparison of values obtained from the NHANES and NIH Toolbox studies, Am J Occup Ther source

      The Results (page unavailable) report significantly higher handgrip strength in males than females. The cited paper does not report a 36% difference or identify participants as cisgender; the adjacent lean-body-mass and knee-extension figures have separate citations and are not judged here. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • cites [61] source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Findingown data

    Twenty-four studies were identified and reviewed.

    “Twenty-four studies were identified and reviewed.”
    • Also stated in: § Search results · plain
      “From an initial yield of 795 articles, 24 studies15–19 36–54 were included in this review.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    Transwomen experienced significant decreases in all parameters measured (lean body mass, muscular area, muscular strength, and haemoglobin/haematocrit) after gender-affirming hormone therapy.

    “Transwomen experienced significant decreases in all parameters measured, with different time courses noted.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingcitation

    Three cross-sectional studies reported that transwomen had 6.4% and 8.0% lower lean body mass than cisgender men and reductions of 4% in lean body mass in transwomen with 12 months of GAHT.

    “These studies reported 6.4% and 8.0% lower LBM than in cisgender men and reductions of 4% in LBM in the transwomen with 12 months of GAHT.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [41] Van Caenegem, 2015, Preservation of volumetric bone density and geometry in trans women during cross-sex hormonal therapy: a prospective observational study, Osteoporos Int source
    • cites [51] source
    • cites [54] source

  • It may state two separate claims as one.

    Findingcitation

    One cross-sectional study reported 9% smaller cross-sectional area in hormone-naive transwomen than in cisgender men, with the transwomen undergoing a further 4% decrease in cross-sectional area with 24 months of GAHT.

    “One study reported 9% smaller CSA in hormone-naive transwomen41 than in cisgender men, with the transwomen undergoing a further 4% decrease in CSA with 24 months of GAHT.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [41] Van Caenegem, 2015, Preservation of volumetric bone density and geometry in trans women during cross-sex hormonal therapy: a prospective observational study, Osteoporos Int source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Findingown data

    The sample sizes of the reviewed studies varied from 12 to 249.

    “The sample sizes of the studies varied from 12 to 249.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingcitation

    In the same study, forearm cross-sectional area was decreased by 8.6% after 12 months, yet at 24 months was 4.4% lower than baseline, indicating that forearm cross-sectional area was 4.2% larger at 24 months than at 12 months.

    “The same study reported that compared with baseline, forearm CSA was decreased by 8.6% after 12 months, yet at 24 months was 4.4% lower than baseline, indicating that forearm CSA was 4.2% larger at 24 months than at 12 months.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [41] Van Caenegem, 2015, Preservation of volumetric bone density and geometry in trans women during cross-sex hormonal therapy: a prospective observational study, Osteoporos Int source

  • It may state two separate claims as one.

    Findingcitation

    In the study finding no significant difference, participants failed to reach typical female testosterone levels after 6 months (mean testosterone=6.9 nmol/L).

    “The participants also failed to reach typical female testosterone levels (after 6 months mean testosterone=6.9 nmol/L)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [47] source

  • It may state two separate claims as one.

    Findingreasoning

    Overall, GAHT in non-athletic transwomen reduces lean body mass, muscle cross-sectional area, muscular strength, and Hgb/HCT over time.

    “Overall, the findings demonstrate a reduction in these parameters over time.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingcitation

    The fifth longitudinal study to assess strength measured upper leg strength using knee flexion and extension and found no significant difference after 12 months.

    “The fifth longitudinal study to assess strength measured upper leg strength using knee flexion and extension and found no significant difference after 12 months.16”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [16] Wiik, 2020, Muscle strength, size, and composition following 12 months of Gender-affirming treatment in transgender individuals, J Clin Endocrinol Metab source

  • It may state two separate claims as one.

    Findingcitation

    Three cross-sectional studies found significant differences (p<0.05) or large effect sizes (Cohen's d=1.0) in HCT between transwomen after 6 months of GAHT and hormone-naive transwomen, with HCT decreases of 7.4%-10.9%.

    “Three cross-sectional studies45 50 52 found significant differences45 50 (p<0.05) or large effect sizes52 (Cohen’s d=1.0) in HCT between transwomen after 6 months of GAHT and hormone-naive transwomen, and HCT decreases of 7.4%–10.9%.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [45] 2012, Altered arterial stiffness in male-to-female transsexuals undergoing hormonal treatment, J Obstet Gynaecol Res source
    • cites [50] Jain, 2019, Medroxyprogesterone acetate in Gender-Affirming therapy for Transwomen: results from a retrospective study, J Clin Endocrinol Metab source
    • cites [52] source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one. The quote only partly states this claim.

    Findingcitation

    In the study finding no significant difference, participants had a mean age of 18 years and a range of 14-25 years.

    “The mean age of participants in the latter study was 18 years and the range was 14–25 years.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [47] source

  • It may state two separate claims as one.

    Findingcitation

    One cross-sectional study found 14% lower hand grip strength in hormone-naive transwomen than in cisgender men (p<0.001) and a further 7% reduction in hand grip strength of the transwomen after 12 months of GAHT.

    “One study found 14% lower hand grip strength in hormone-naive transwomen than in cisgender men (p<0.001)41 and a further 7% reduction in hand grip strength of the transwomen after 12 months of GAHT.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [41] Van Caenegem, 2015, Preservation of volumetric bone density and geometry in trans women during cross-sex hormonal therapy: a prospective observational study, Osteoporos Int source

  • It may state two separate claims as one.

    Findingcitation

    Overall, this review reports decreases in muscle strength, lean body mass, and muscle cross-sectional area in response to 12-36 months of GAHT in transwomen.

    “Overall, this review reports decreases in muscle strength, LBM and muscle CSA in response to 12–36 months”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    World Athletics requires that transgender athletes and athletes with differences of sexual development have testosterone levels ≤5 nmol/L in order to be eligible for the female category.

    “Presently, World Athletics requires that transgender athletes5 and athletes with differences of sexual development6 have testosterone levels ≤5 nmol/L in order to be eligible for the female category.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [5] World Athletics . Eligibility regulations transgender regulation, 2019. Available: https://www.worldathletics.org/about-iaaf/documents/book-of-rules

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [6] World Athletics . Eligibility regulations for the female classification, 2019. Available: https://www.worldathletics.org/about-iaaf/documents/book-of-rules

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim.

    Study design and conductcitation

    Each study was examined for quality in line with the Effective Public Health Practise Project (EPHPP) tool.

    “Each study was initially categorised based on its design (eg, cohort, case–control) and examined for quality in line with the Effective Public Health Practise Project (EPHPP) tool.33”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [33] source

  • It may state two separate claims as one.

    Premisecitation

    Myonuclei number is increased with training and with use of anabolic steroids.

    “Myonuclei number is increased with training and with use of anabolic steroids.28”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [28] source

  • It may state two separate claims as one.

    Study design and conductreasoning

    The high post-GAHT testosterone is a possible confounder, and potential physiological differences between adolescent and adult participants may also confound results.

    “The high post-GAHT testosterone is a possible confounder, and potential physiological differences between adolescent and adult participants may also confound results.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    The EPHPP tool is suitable for use in systematic reviews and has content and construct validity.

    “This is a generic tool used to evaluate a variety of intervention study designs and is suitable for use in systematic reviews,34 having content and construct validity.35”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [34] Storebø, 2018, Methylphenidate for attention deficit hyperactivity disorder (ADHD) in children and adolescents - assessment of adverse events in non-randomised studies, Cochrane Database Syst Rev source
    • cites [35] source

  • It may state two separate claims as one.

    Interpretationreasoning

    The effects of GAHT on body composition, muscle strength, and Hgb/HCT parameters, or athletic performance in transgender people who engage in training and competition, remain unknown.

    “the effects of GAHT on these parameters, or indeed athletic performance in transgender people who engage in training and competition, remain unknown.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Changes in body composition, muscle strength, and Hgb/HCT in non-athletic transwomen are informative about athletic performance in transwomen athletes.

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    The levels of physical activity of the transwomen compared with cisgender women in the studies were not reported.

    “The levels of physical activity of the transwomen compared with cisgender women in the studies were not reported.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    The studies included in the review were written in English only.

    “Other limitations include the studies being written in English only”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationreasoning

    These observations in trained transgender individuals are consistent with the findings of the current review in untrained transgender individuals, whereby 30 months of GAHT may be sufficient to attenuate some, but not all, influencing factors associated with muscular endurance and performance.

    “These observations in trained transgender individuals are consistent with the findings of the current review in untrained transgender individuals, whereby 30 months of GAHT may be sufficient to attenuate some, but not all, influencing factors associated with muscular endurance and performance.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Changes in body composition, muscle strength, and Hgb/HCT in non-athletic transwomen are informative about athletic performance in transwomen athletes.

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductnone given

    This review only focused on binary transgender individuals and did not consider non-binary individuals.

    “This review only focused on binary transgender individuals”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Study design and conductreasoning

    The overlap of participants in the ENIGI studies and the heterogenous methodology in the other studies precluded meaningful meta-analysis.

    “the overlap of participants in the ENIGI studies and the heterogenous methodology in the other studies precluded the possibility of meaningful meta-analysis.”
    Quote in the paperSubstantial claim
34 of 34

  • The paper relies on this without support.

    The performance-related differences between transwomen who have received gender-affirming hormone treatment and cisgender women are less clear.

    “In contrast, the performance-related differences between transwomen who have received gender affirming hormone treatment (GAHT) and cisgender women are less clear.”

  • The paper relies on this without support.

    No prospective studies have investigated changes in athletic performance in transgender athletes after hormonal transition.

    “To date, there have been no prospective studies investigating the changes in athletic performance in transgender athletes after hormonal transition.”

  • The paper relies on this without support.

    The effects of testosterone suppression on physiology, and the time course in which these changes occur, are less clear.

    “While it is known that testosterone levels are markedly reduced in transgender women taking testosterone suppressing GAHT,29 the effects of this hormonal change on physiology, and the time course in which these changes occur, are less clear.”

  • The paper relies on this without support.

    Lean body mass, muscle cross-sectional area, muscular strength, and Hgb/HCT are strongly associated with athletic performance.

    “four characteristics strongly associated with athletic performance: LBM, muscle CSA, muscular strength, and Hgb/ HCT levels.”

  • The paper relies on this without support.

    Changes in body composition, muscle strength, and Hgb/HCT in non-athletic transwomen are informative about athletic performance in transwomen athletes.

    “We summarise changes induced by GAHT in non-athletic transwomen in four characteristics strongly associated with athletic performance: LBM, muscle CSA, muscular strength, and Hgb/ HCT levels.”

  • The paper relies on this without support.

    There is much debate on whether and when transwomen should be permitted to compete in the female category in sport.

    “There is much debate on whether (and when) transwomen should be permitted to compete in the female category in sport.”
6 of 6

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Reported study-size range excludes an included study

    Minor

    The stated maximum study size is 249, but table 1 lists 277 transwomen in the Jain et al study.

  • Lapauw control-group size differs between tables

    Minor

    Table 1 lists 20 cisgender men for Lapauw et al, while table 2 lists 46 for the same study. Tables 3 and 4 also list 46.

2 of 2

Citations

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. Hutcheon D . Hyperandrogenism in athletics: a review of Chand V. IAAF. law in sport, 2015. Available: https://www.lawinsport.com/topics/item/hyperandrogenism-in-athletics-a-review-of-chand-v iaaf

Cited by

Sorted by citations

Related

Metadata

Authors
Harper, J., O'Donnell, E., Sorouri Khorashad, B., McDermott, H., & Witcomb, G. L.
Affiliations
Loughborough University (GB)
Corresponding author
Witcomb, Gemma L
ORCID
Venue
British Journal of Sports Medicine
Publisher
BMJ
Published
2021-03-01
Volume
55
Issue
15
Pages
865-872
ISSN
  • 0306-3674 (ISSN-L)
  • 1473-0480
DOI
10.1136/bjsports-2020-103106
PMC
PMC8311086
OpenAlex
W3134761747
Cited by
206
References
65
Citations by year
2026: 49 · 2025: 44 · 2024: 33 · 2023: 43 · 2022: 22 · 2021: 15
FWCI
3.93
Type
journal article
Language
en
Open access
Licence
Locations
  • British Journal of Sports Medicine (publishedVersion, cc-by-nc)
  • PubMed Central (publishedVersion, cc-by-nc)
  • PubMed (publishedVersion)
  • Loughborough University Research Repository (Loughborough University) (submittedVersion, cc-by-nc)
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Hormonal and reproductive studies
  • Social Sciences › Psychology › Social Psychology › LGBTQ Health, Identity, and Policy
  • Social Sciences › Gender Studies › Sports, Gender, and Society
Keywords
transgender women, gender-affirming hormone therapy, testosterone suppression, body composition, lean body mass, muscle strength, muscle area, hemoglobin, hematocrit, sports participation
MeSH terms
Adipose Tissue, Androgen Antagonists, Body Composition, Estradiol, Female, Hematocrit, Hemoglobin A, Humans, Male, Sports, Testosterone, Time Factors, Transsexualism, Cyproterone Acetate, Muscle, Skeletal, Muscle Strength, Athletic Performance, Transgender Persons

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

A language model drew the claims from the paper on 2026-10-09, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

A second model labelled each claim on 2026-10-09 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).

Cited sources are checked with a language model’s help (gpt-6-sol).

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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