A year of lower testosterone is enough to make transgender women's sports advantage fair, the claim says.

See the scientific wording

In transgender women, a one-year reduction in testosterone (method of reduction, target testosterone levels, and baseline levels not reported) is sufficient to reduce their competitive advantage in women's sports to a level considered acceptable for fair competition (the specific competitive-advantage threshold or acceptable fairness criterion is not defined or reported). No absolute or relative effect size for the reduction in competitive advantage is reported.

Supporting

Low

1 study

Contradicting

Low

2 studies

There's disagreement

Observational

The 3 studies we reviewed point in different directions — there's no clear consensus.

What the research says

3 studies reviewed

Supporting (1)

Low

A unique pseudo-eligibility analysis of longitudinal laboratory performance data from a transgender female competitive cyclist
Cohort StudyHuman
A single transgender cyclist’s lab tests moved toward female ranges after a year of hormone therapy, suggesting she might compete fairly. But this is only one athlete and not strong enough to prove that one year always makes competition fair.

Contradicting (2)

Low

Testosterone Levels in Transgender Women Undergoing Gender-Affirming Hormone Therapy
Cohort StudyHuman2025
The study looked at testosterone levels in transgender women on hormone therapy. It found that after one year, many had low testosterone, but about a quarter still had levels above common sports limits, and it didn't measure whether sports fairness was achieved.
The International Olympic Committee framework on fairness, inclusion and nondiscrimination on the basis of gender identity and sex variations does not protect fairness for female athletes
Editorial/Opinion2024
The claim says one year of lower testosterone makes transgender women's sports advantage fair. The study says no: after a year, most of the male advantage remains, so it is not enough for fair competition.

Quality-weighted scoring: we follow the GRADE framework — each study is rated High, Moderate, Low, or Very Low based on study design, methodology rigor, and risk of bias. A single high-quality RCT can outweigh several weaker observational studies.

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Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting, 2 contradicting studies

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