Serum inhibin B concentration in a prepubertal boy with gynecomastia and Peutz-Jeghers syndrome.

Gynecomastia in boys with Peutz-Jeghers syndrome and Sertoli cell tumors of gonadal origin results from increased estrogen production due to increased aromatase activity within the testicular tumor. We present a prepubertal boy with Peutz-Jeghers syndrome, gynecomastia and bilateral neoplastic Sertoli cell proliferation in whom the only abnormal hormonal profile was increased concentration of inhibin B and Pro-alpha C in serum.