Gynecomastia in adolescence is a benign condition that mostly disappears spontaneously within approximately two years from onset. When it is associated with hypogonadism, it may suggest a disorder of sexual differentiation. We report the case of a young man (18 years old) with gynecomastia associated with azoospermia, small testes, hyperestrogenism and hypergonadotropic hypogonadism. A karyotype 46,XX was found, and searching for SRY (sex-determining region Y) by fluorescence in situ hybridization (FISH) highlighted the presence of the gene on the terminal region of the short arm, with breakpoints likely in Xp22.3 and Yp11.3. Implications of testosterone replacement therapy with respect to sex differentiation disorder and to physical performance are discussed.
