A 17 year old male presents to the clinic complaining that he has
not begun to shave unlike his friends at school. He gives a history of having
had undescended testes treated by orhidopexy. On examination you note that he
has poorly developed secondary sexual characteristics and gynaecomastia.
Investigations reveal a high level of beta- human chorionic gonadotrophin
In this patient which one of the following investigations would you