Which of the following is the most common cause of hypergonadotrophic hypogonadism in males:

Klinefelter's syndrome is the most common cause of hypergonadotrophic hypogonadism in males. Karyotype is XXY. Patients present with infeility or delayed sexual maturation or hypogonadism. Affected males have small testes, and variable degree of androgen deficiency which manifest as gynecomastia or scanty beard growth. Azoospermia or oligospermia are present. Urinary gonadotropin levels are raised. Ref: Physiology secrets By Hershel Raff page 242; Cancer and Sexual Health By John P. Mulhall page 197; Organic psychiatry: the psychological consequences of cerebral disorder By William Alwyn Lishman page 526; Manual of Endocrinology and Metabolism By Norman Lavin page 292; The immunoassay handbook By David Wild page 567