[HCG producing malignant teratoma of the testis: a rare cause of precocious isosexual maturation in boys].

Human chorionic gonadotropin (HCG) from a testicular tumor histologically diagnosed from its metastases to be a malignant teratoma induced elevated testosterone levels and subsequent precocious isosexual development in a 12-year-old boy. The endocrinologic consequences of long term ectopic HCG production in the prepubertal male are discussed. The case report illustrates the value of HCG serum levels as a marker for tumor activity.