RecruitingPhase 1NCT07718997
Rare condition
Klinefelter Syndrome
Also known as 47, XXY syndrome, XXY male
Klinefelter syndrome (47,XXY) is the most common sex chromosome disorder in males, characterised by an extra X chromosome. It affects testosterone production, fertility, and development.
Gene Extra X chromosome (47Gene XXY karyotype)Prevalence 1 in 500–1,000 male birthsOnset Congenital (47,XXY karyotype)
7
studies recruiting now
as of 7 Sept 2026
46
studies registered in total
as of 7 Sept 2026
5
countries with a recruiting site
as of 7 Sept 2026
22 Jul 2026
most recent study posted
among recruiting studies
Recruiting trials
RecruitingPhase 3NCT05586802
Sex Steroids Balance for Metabolic and Reproductive Health in Klinefelter Syndrome
RecruitingNCT05581147
Thyroid Function and Structure in Klinefelter Syndrome
RecruitingPhase 4NCT06294990
Klinefelter Syndrome and Testosterone Treatment in Puberty
RecruitingNCT03396562
The eXtroardinarY Babies Study: Natural History of Health and Neurodevelopment in Infants and Young Children With Sex Chromosome Trisomy
Showing the 5 most recently updated recruiting studies, as recorded 7 Sept 2026. Live status on each study page.
See all 7 recruiting studiesWhere recruiting studies are running
Countries with at least one recruiting site among the studies above, 7 Sept 2026. Tap a country to search trials there.
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About Klinefelter Syndrome
Klinefelter syndrome (47,XXY) is the most common sex chromosome disorder in males, characterised by an extra X chromosome. It affects testosterone production, fertility, and development. Most individuals are not diagnosed until puberty or adulthood when fertility issues or testosterone deficiency become apparent. Testosterone replacement therapy (TRT) is the cornerstone of treatment. Clinical trials are investigating fertility preservation, early testosterone intervention, and bone density outcomes. The syndrome is substantially underdiagnosed — estimated 75% of affected males are never diagnosed.
Common clinical features
Small testes (hypogonadism)Infertility (azoospermia)Reduced testosteroneTall stature with long limbsGynaecomastiaReduced facial and body hairLearning and language difficultiesAnxiety and depression
From Orphanet’s phenotype annotations (CC BY 4.0). Not a complete list.
Before you apply
Things trial teams commonly ask about for Klinefelter Syndrome. Not eligibility rules; those are set by each study.
- Klinefelter syndrome is diagnosed by karyotype (chromosomal analysis) — a standard blood test can confirm 47,XXY.
- Micro-TESE (testicular sperm extraction) is available to some Klinefelter males with azoospermia and is offered through specialised fertility centres — clinical trials are assessing fertility preservation timing.
- The American Association for Klinefelter Syndrome Information and Support (AAKSIS) connects individuals to research programmes and peer networks.
Related conditions
Information, not medical advice. Trial listings are shown as recorded on ClinicalTrials.gov; whether any study is right for you is a decision for you and your clinicians, and eligibility is decided by each research team. Disease information from Orphanet (CC BY 4.0).