Clinical Research Directory

Inclusion Criteria: * Patients with a confirmed diagnosis of classic, non-mosaic 47,XXY Klinefelter syndrome based on a peripheral blood 97 karyotype analysis; * Availability of thyroid function test results (TSH, fT3, and fT4) and/or thyroid US imaging; * Availability of concurrent clinical data. Exclusion Criteria: * Presence of other known genetic conditions or chromosomal abnormalities; * Use of levothyroxine or other drugs that are either active on the hypothalamic-pituitary-thyroid (HPT) axis or that may interfere with thyroid function tests; * History of previous surgery or radiotherapy on the thyroid or pituitary glands; * Current or previous T therapy (for the pre-pubertal and pubertal groups).