Title: Klinefelter syndrome
Long Title: IUPAC Gold Book - Klinefelter syndrome
DOI: 10.1351/goldbook.10877
Status: current

Definition
Syndrome in males resulting from a genetic defect in which an extra female X chromosome (thus an XXY genotype) is present in a male, characterized by small testes, long legs, enlarged breasts, reduced sperm production, and mental retardation.

Related Terms
- Syndrome: https://goldbook.iupac.org/terms/view/11277
- X chromosome: https://goldbook.iupac.org/terms/view/11385
- sperm: https://goldbook.iupac.org/terms/view/11243
- testes: https://goldbook.iupac.org/terms/view/11295

Source
- PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 771 (https://doi.org/10.1515/pac-2015-1202)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/10877/html
- json: https://goldbook.iupac.org/terms/view/10877/json
- xml: https://goldbook.iupac.org/terms/view/10877/xml

Citation: Citation: 'Klinefelter syndrome' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.10877
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Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-06-14T01:20:10+00:00